radeonsi: fix calculation of valid RB mask per SE
radeonsi: fix calculation of valid RB mask per SE

The old calculation treated too many RBs as disabled.

Cc: 11.0 11.1 11.2 12.0 <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>
Reviewed-by: Alex Deucher <08dc22c6156113f2deff178e35e3ed9b24d6af9e@amd.com>
Reviewed-by: Marek Olšák <8c7344a1abdb103e79ecfd488098373070c3c70e@amd.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler