radeonsi: fix perfcounter selection for SI_PC_MULTI_BLOCK layouts
radeonsi: fix perfcounter selection for SI_PC_MULTI_BLOCK layouts

The incorrectly computed register count caused lockups.

Reviewed-by: Edward O'Callaghan <117173807d5a49976a891944633465c0daea7f98@alterapraxis.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler