vdso32: Drop implicit common-page-size linker flag

These are implied by the target architecture and for x86_64 match the
max-page-size. The default for non-NaCl x86_64 is 0x1000 (4096).

In bfd the common page size is defined as 0x1000 (4096) for non-NaCl
x86_64 targets:

bfd/elf64-x86-64.c:
4998:#define ELF_COMMONPAGESIZE             0x1000

For gold, the common page size is defined as 0x1000 (4096) for non-NaCl
x86_64 targets:

gold/x86_64.cc:
1413:  0x1000, // common_pagesize (overridable by -z common-page-size)
1442:  0x1000, // common_pagesize (overridable by -z common-page-size)

(ELF_COMMONPAGESIZE also defaults to ELF_MAXPAGESIZE when not set
explicitly for a target architecture in bfd/elfxx-target.h, but that's
not relevant for x86_64).

Because it's implied by the target architecture, it's of questionable
use to implement in LLD.  This patch resolves one of the issues towards
using LLD to link an x86_64 kernel.

Fixes commit 2aae950 ("x86_64: Add vDSO for x86-64 with
gettimeofday/clock_gettime/getcpu")

Change-Id: If8c517223f705dc5d2dac43ebeb1fac1c6a9d484
Link: https://bugs.llvm.org/show_bug.cgi?id=38774
Link: ClangBuiltLinux/linux#31
Cc: Fangrui Song <maskray@google.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Reported-by: Dmitry Golovin <dima@golovin.in>
Reported-by: Bill Wendling <morbo@google.com>
Suggested-by: Dmitry Golovin <dima@golovin.in>
Suggested-by: Rui Ueyama <ruiu@google.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Adam W. Willis <return.of.octobot@gmail.com>
Signed-off-by: mcdachpappe <noreference@web.de>

arch/arm/vdso/Makefile

@@ -10,8 +10,7 @@ ccflags-y := -fPIC -fno-common -fno-builtin -fno-stack-protector
 ccflags-y += -DDISABLE_BRANCH_PROFILING
 
 ldflags-y = -Bsymbolic --no-undefined -soname=linux-vdso.so.1 \
-	    -z max-page-size=4096 -z common-page-size=4096 \
-	    -nostdlib -shared \
+	    -z max-page-size=4096 -nostdlib -shared \
 	    $(call ld-option, --hash-style=sysv) \
 	    $(call ld-option, --build-id) \
 	    -T