[AMDGPU] Introduce optimizeCompareInstr

The following patterns are currently handled:

s_cmp_eq_u32 (s_and_b32 $src, 1), 1 => s_and_b32 $src, 1
s_cmp_eq_i32 (s_and_b32 $src, 1), 1 => s_and_b32 $src, 1
s_cmp_eq_u64 (s_and_b64 $src, 1), 1 => s_and_b64 $src, 1
s_cmp_ge_u32 (s_and_b32 $src, 1), 1 => s_and_b32 $src, 1
s_cmp_ge_i32 (s_and_b32 $src, 1), 1 => s_and_b32 $src, 1
s_cmp_lg_u32 (s_and_b32 $src, 1), 0 => s_and_b32 $src, 1
s_cmp_lg_i32 (s_and_b32 $src, 1), 0 => s_and_b32 $src, 1
s_cmp_lg_u64 (s_and_b64 $src, 1), 0 => s_and_b64 $src, 1
s_cmp_gt_u32 (s_and_b32 $src, 1), 0 => s_and_b32 $src, 1
s_cmp_gt_i32 (s_and_b32 $src, 1), 0 => s_and_b32 $src, 1

Differential Revision: https://reviews.llvm.org/D109031