[AMDGPU][MC] Enables sgpr or imm src1 for float VOP3 DPP, but excludi… (#87382)

…ng VOPC.

Fixes support on GFX1150 and GFX12 where src1 of e64_dpp instructions
should allow sgpr and imm operands.
PR #67461 added support for this with int operands, but it was missing a
piece for float.
Changing VOPC e64_dpp will be in a different patch because there is a
bug preventing that change.