intel/blorp: Add a shader type to make keys more unique

intel/blorp: Add a shader type to make keys more unique

Depending on how the driver using blorp implements its shader caching,
there is a small chance of shader collisions due to identical keys between
blit and clear programs.  Adding a small shader type at the top of the key
alleviates this problem.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>