pvr: use strongly-typed enum instead of uint32_t

Acked-by: Ashish Chauhan <Ashish.Chauhan@imgtec.com>
Acked-by: Frank Binns <frank.binns@imgtec.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38832>

src/imagination/vulkan/pvr_formats.c

@@ -210,7 +210,7 @@ static const struct pvr_format pvr_format_table[] = {
    }
 
 struct pvr_pbe_format {
-   uint32_t packmode;
+   enum ROGUE_PBESTATE_PACKMODE packmode;
    enum pvr_pbe_accum_format accum_format;
 };