[AMDGPU] Fix image_msaa_load waitcnt insertion for pre-gfx12 (#90710)

https://github.com/llvm/llvm-project/pull/90201 made some fixes for
gfx12
image_msaa_load waitcnt insertion.
That fix might break in some situations for pre-gfx12 - this fixes that
by
explitly checking for VSAMPLE which always requires a s_wait_samplecnt
and
leaves the previous logic intact for non-gfx12.