Update for cppcheck v1.80

[behlendorf]

Description

Resolve new warnings and errors from cppcheck v1.80.

• Possible null pointer dereference: protocol
• Possible null pointer dereference: srctype
• Uninitialized variable: link
• [module/zfs/abd.c:353]: (error) Uninitialized variable: sg
• [module/zfs/abd.c:353]: (error) Uninitialized variable: i
• [module/zfs/abd.c:385]: (error) Uninitialized variable: sg
• [module/zfs/abd.c:385]: (error) Uninitialized variable: i
• [module/zfs/abd.c:553]: (error) Uninitialized variable: i
• [module/zfs/abd.c:553]: (error) Uninitialized variable: sg
• [module/zfs/abd.c:763]: (error) Uninitialized variable: i
• [module/zfs/abd.c:763]: (error) Uninitialized variable: sg
• [module/zfs/abd.c:305]: (error) Uninitialized variable: tmp_page
• Possible null pointer dereference: value
• [module/zfs/zvol.c:208]: (error) Uninitialized variable: p

Convert the following suppression to inline.

• Possible null pointer dereference: aiov

Exclude HAVE_UIO_ZEROCOPY and HAVE_DNLC from analysis since
these macro's will never be defined until this functionality
is implemented.

Motivation and Context

Preparation for upgrading buildbot to use cppcheck v1.80.

How Has This Been Tested?

make lint locally with cppcheck v1.72 and v1.80. No warnings or errors reported.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the ZFS on Linux code style requirements.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.
• All commit messages are properly formatted and contain Signed-off-by.
• Change has been approved by a ZFS on Linux member.

[codecov]

Codecov Report

Merging #6879 into master will decrease coverage by 0.07%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #6879      +/-   ##
=========================================
- Coverage   75.28%   75.2%   -0.08%     
=========================================
  Files         298     298              
  Lines       95268   95269       +1     
=========================================
- Hits        71725   71651      -74     
- Misses      23543   23618      +75

Flag	Coverage Δ
#kernel	74.53% <100%> (ø)	⬆️
#user	67.4% <100%> (-0.17%)	⬇️

Impacted Files	Coverage Δ
module/zfs/zvol.c	84.16% <ø> (-1%)	⬇️
module/zfs/zfs_vnops.c	63.12% <ø> (+0.37%)	⬆️
lib/libzfs/libzfs_import.c	73.39% <100%> (-0.08%)	⬇️
module/zfs/abd.c	99.19% <100%> (ø)	⬆️
module/zfs/zpl_xattr.c	78.18% <100%> (ø)	⬆️
lib/libshare/libshare.c	66.96% <100%> (-0.2%)	⬇️
lib/libzfs/libzfs_dataset.c	74.31% <100%> (+0.01%)	⬆️
module/zfs/ddt.c	91.03% <0%> (-5.2%)	⬇️
module/zfs/dsl_scan.c	84.58% <0%> (-2.3%)	⬇️
module/zfs/arc.c	86.82% <0%> (-1.82%)	⬇️
... and 44 more

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