st/dri: support format queries

st/dri: support format queries

ask the driver for supported dmabuf formats

v2: rebase to master.
v3: return false on failure.
v4: use pscreen->is_format_supported instead of adding a new query.
    (Lucas Stach)
v5: stylefix to conform to formatting rules (Brian Paul). add fourcc list
    here instead of using struct image_format from v4.

Signed-off-by: Varad Gautam <varad.gautam@collabora.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de> (v4)
Cc: Lucas Stach <l.stach@pengutronix.de>