two routines (one for G200 and one for G400) were replaced with static
const variables and a single function that returns the correct size.
The code to generate an error if the allocated WARP region is too small
was refactored from mga_warp_install_{g200,g400}_microcode to
mga_wrap_install_microcode.
mga_warp_microcode_size is global to the MGA DRM because it will soon be
used by code in another file.