radeonsi: Program RASTER_CONFIG for harvested GPUs v5

radeonsi: Program RASTER_CONFIG for harvested GPUs v5

Harvested GPUs have some of their render backends disabled, so
in order to prevent the hardware from trying to render things
with these disabled backends we need to correctly program
the PA_SC_RASTER_CONFIG register.

v2:
  - Write RASTER_CONFIG for all SEs.

v3:
  - Set GRBM_GFX_INDEX.INSTANCE_BROADCAST_WRITES bit.
  - Set GRBM_GFX_INFEX.SH_BROADCAST_WRITES bit when done setting
    PA_SC_RASTER_CONFIG.
  - Get num_se and num_sh_per_se from kernel.

v4:
  - Get correct value for num_se
  - Remove loop for setting PA_SC_RASTER_CONFIG
  - Only compute raster config when a backend has been disabled.

v5: Michel Dänzer
  - Fix computation for chips with multiple SEs

https://bugs.freedesktop.org/show_bug.cgi?id=60879

CC: "10.4 10.3" <mesa-stable@lists.freedesktop.org>