mesa/formats: only do type and component lookup for uncompressed formats

mesa/formats: only do type and component lookup for uncompressed formats

Only uncompressed formats have a non-void type and actual
components per pixel. Rename _mesa_format_to_type_and_comps
to _mesa_uncompressed_format_to_type_and_comps and require
callers to check if the format is not compressed.

v2. include compressed format cases to avoid gcc warnings (Chad).

Reviewed-by: Chad Versace <chad.versace@intel.com>
Signed-off-by: Nanley Chery <nanley.g.chery@intel.com>