i965/dri: Support R8G8B8A8 and R8G8B8X8 configs

i965/dri: Support R8G8B8A8 and R8G8B8X8 configs

The Android framework requires support for EGLConfigs with
HAL_PIXEL_FORMAT_RGBX_8888 and HAL_PIXEL_FORMAT_RGBA_8888.

Even though all RGBX formats are disabled on gen9 by
brw_surface_formats.c, the new configs work correctly on Broxton thanks
to _mesa_format_fallback_rgbx_to_rgba().

On GLX, this creates no new configs, and therefore breaks no existing
apps. See in-patch comments for explanation. I tested with glxinfo and
glxgears on Skylake.

On Wayland, this also creates no new configs, and therfore breaks no
existing apps. (I tested with mesa-demos' eglinfo and es2gears_wayland
on Skylake). The reason differs from GLX, though. In
dri2_wl_add_configs_for_visual(), the format table contains only
B8G8R8X8, B8G8R8A8, and B5G6B5; and dri2_add_config() correctly matches
EGLConfig to format by inspecting channel masks.

On Android, in Chrome OS, I tested this on a Broxton device. I confirmed
that the Google Play Store's EGLSurface used HAL_PIXEL_FORMAT_RGBA_8888,
and that an Asteroid game's EGLSurface used HAL_PIXEL_FORMAT_RGBX_8888.
Both apps worked well. (Disclaimer: I didn't test this patch on Android
with Mesa master. I backported this patch series to an older Android
branch).

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>