arch-power: Fix compare instructions

arch-power: Fix compare instructions

Now that 64-bit registers are being used, instead of always
performing a 32-bit comparison, these instructions must use
the L field to determine the type of comparison to be made.
The comparison can either be 32-bit or 64-bit. This fixes
the following instructions.
  * Compare (cmp)
  * Compare Logical (cmpl)
  * Compare Immediate (cmpi)
  * Compare Logical Immediate (cmpli)

Change-Id: Ia7655ffa463214c24e094e01d4188decf6486904
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>