gallium/winsys/kms: Fix dumb buffer bpp

The bpp in the dumb buffer creation request is hardcoded to 32, which is an incorrect assumption as the caller is free to pick any pipe format. Use the bpp supplied to us through util_format_get_blocksizebits().

Fixes: 3b176c44 "gallium: Add a dumb drm/kms winsys backed swrast provider" Signed-off-by: Kevin Strasser kevin.strasser@intel.com Reviewed-by: Adam Jackson ajax@redhat.com Reviewed-by: Marek Olšák marek.olsak@amd.com