dri: Convert driCreateConfigs to use a gl_format enum

dri: Convert driCreateConfigs to use a gl_format enum

This is instead of the pair of GLenums for format and type that were
previously used.  This is necessary for the Intel drivers to expose sRGB
framebuffer formats.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>