intel: Fix format handling of blit glBitmap()

intel: Fix format handling of blit glBitmap()

Any 32-bit format got ARGB8888 handling (including, say, GL_RG1616), and
anything else got 16-bit (including, say, GL_R8), which could potentially
hang the GPU by writing out of bounds.

NOTE: This is a candidate for the stable branches.

Reviewed-and-tested-by: Ian Romanick <ian.d.romanick@intel.com>
Acked-by: Paul Berry <stereotype441@gmail.com>