radeonsi: Enable VGPR spilling for all shader types v5

radeonsi: Enable VGPR spilling for all shader types v5

v2:
  - Only emit write SPI_TMPRING_SIZE once per packet.
  - Use context global scratch buffer.

v3:
  - Patch shaders using WRITE_DATA packet instead of map/unmap.
  - Emit ICACHE_FLUSH, CS_PARTIAL_FLUSH, PS_PARTIAL_FLUSH, and
    VS_PARTIAL_FLUSH when patching shaders.

v4:
  - Code cleanups.
  - Remove unnecessary multiplies.

v5:
  - Patch shaders in system memory and re-upload to vram.

Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>