frontends/va: improve surface attribs processing

frontends/va: improve surface attribs processing

Instead of checking whether the attribute is settable for each
attrib type, check that once at the beginning of the loop.

Instead of having an if for each attrib type, use a switch.

Return an error if we encounter an unknown attribute. This allows
the caller to make sure settable attributes aren't ignored. The
intel media driver seems to just assert [1] that it doesn't encounter
unknown attributes.

[1]: https://github.com/intel/media-driver/blob/95d413e519a980f6a7178880ccbfedace092316c/media_driver/linux/common/ddi/media_libva.cpp#L2530

Signed-off-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10104>