radeonsi: remove a workaround for inexact *8_SNORM blits
radeonsi: remove a workaround for inexact *8_SNORM blits

All tests pass on Fiji now. This prevents DCC disablement due to
incompatible DCC formats due to the fallback.

Reviewed-by: Nicolai Hähnle <0d0be6cf5ad662651be2dc5dfd44aa2b09d4c1cc@amd.com>
Tested-by: Edmondo Tommasina <9e91d6b21d26a489d8e8a656718247cfcec7b511@gmail.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler