arch-power: Add fields for D and X form instructions
arch-power: Add fields for D and X form instructions

This adds the L field for D and X form instructions that
specifies if a compare instruction should perform 32-bit
or 64-bit comparison of its operands.

Change-Id: I72413a507c93096b1573836197837227c1c1e521
Signed-off-by: Sandipan Das <ae8113f64d9c72812e097938d25a8975da69c074@linux.ibm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/40911
Reviewed-by: Boris Shingarov <9e9a86074d235a5ecff50c3f2485c8b344969b31@labware.com>
Maintainer: Boris Shingarov <9e9a86074d235a5ecff50c3f2485c8b344969b31@labware.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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