amd/common: use SH{0,1}_CU_EN definitions only of COMPUTE_STATIC_THREAD_MGMT_SE0

amd/common: use SH{0,1}_CU_EN definitions only of COMPUTE_STATIC_THREAD_MGMT_SE0

The automatic header generation unifies identical registers in a series
and only emits definitions for the first one. This is mostly to avoid
emitting excessive definitions for CB registers, but special-casing
an exception for this family of registers doesn't seem worth it.