gallium/util: use enum pipe_prim_type instead of unsigned some more
gallium/util: use enum pipe_prim_type instead of unsigned some more

There were complaints from a mingw build:
u_draw.h:134:14: error: invalid conversion from ‘uint {aka unsigned int}’
to ‘pipe_prim_type’ [-fpermissive]

Reviewed-by: Brian Paul <3cb4e1df5ec4da2c7c4af7c52cec8cf340a55a10@vmware.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler