This new function to get the drm_format associated with a pixman
format will be useful while creating a dmabuf.

Based-on-patch-by: Gerd Hoffmann <kraxel@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Message-Id: <20210526231429.1045476-11-vivek.kasireddy@intel.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>