drm/vmwgfx: Cleanup kms setup without 3d

Do not validate format equality for the non 3d cases to allow xrgb to
argb copies and make sure the dx binding flags are only used
on dx compatible surfaces.

Fixes basic 2d kms setup on configurations without 3d. There's little
practical benefit to it because kms framebuffer coherence is disabled
on configurations without 3d but with those changes the code actually
makes sense.

v2: Remove the now unused format variable

Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Fixes: d6667f0d ("drm/vmwgfx: Fix handling of dumb buffers")
Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list@broadcom.com>
Cc: dri-devel@lists.freedesktop.org
Cc: <stable@vger.kernel.org> # v6.9+
Cc: Maaz Mombasawala <maaz.mombasawala@broadcom.com>
Cc: Martin Krastev <martin.krastev@broadcom.com>
Reviewed-by: Martin Krastev <martin.krastev@broadcom.com>
Reviewed-by: Maaz Mombasawala <maaz.mombasawala@broadcom.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240827043905.472825-1-zack.rusin@broadcom.com