target-ppc: Correct Simple VSR LE Host Inversions

A common pattern in the VSX helper code macros is the use of "x.fld[i]" where
"x" is a VSR and "fld" is an argument to a macro ("f64" or "f32" is passed).
This is not always correct on LE hosts.

This change addresses all instances of this pattern to be "x.fld" where "fld" is:

  - "VsrD(0)" for scalar instructions accessing 64-bit numbers
  - "VsrD(i)" for vector instructions accessing 64-bit numbers
  - "VsrW(i)" for vector instructions accessing 32-bit numbers

Note that there are no instances of this pattern where a scalar instruction
accesses a 32-bit number.

Note also that it would be correct to use "VsrD(i)" for scalar instructions since
the loop index is only ever "0".  I have choosen to use "VsrD(0)" instead ... it
seems a little clearer.

Signed-off-by: Tom Musta <tommusta@gmail.com>
Tested-by: Tom Musta <tommusta@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>