st/mesa: Allocate full miplevels if MaxLevel is explicitly set

st/mesa: Allocate full miplevels if MaxLevel is explicitly set

Some applications explicitly call glTex[ture]Parameteri[v] to set
GL_TEXTURE_MAX_LEVEL and GL_TEXTURE_BASE_LEVEL before uploading any
texture data.  Core Mesa initializes MaxLevel to 1000, so if it isn't
that, we know they've set it.  (We check for < TEXTURE_MAX_LEVELS to
avoid hardcoding that value, however.)

If MaxLevel - BaseLevel > 0, then the app is trying to tell us that
this texture is going to have multiple miplevels.  In that case, go
ahead and allocate the space for it.

Avoids many resource_copy_region calls at texture finalization time
in the Civilization VI benchmark.

Reviewed-by: Michel Dänzer <mdaenzer@redhat.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3401>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3401>