mesa: support GL_RGB for GL_EXT_texture_type_2_10_10_10_REV

mesa: support GL_RGB for GL_EXT_texture_type_2_10_10_10_REV

Commit 8ec6534 changed texture upload path and the way how texture
format is being checked, this commit adds support for GL_RGB with
GL_UNSIGNED_INT_2_10_10_10_REV as specified by the extension
EXT_texture_type_2_10_10_10_REV specification.

This fixes regression in ES3 conformance test
   ES3-CTS.gtf.GL3Tests.packed_pixels.packed_pixels

v2: add MESA_FORMAT_R10G10B10X2_UNORM format (Iago Toral)

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=88385
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>