intel/isl: Add an isl_swizzle structure and use it for isl_view swizzles

This should be more compact than the enum isl_channel_select[4] that we
were using before.  It's also very convenient because we already had such a
structure in the Vulkan driver we just needed to pull it over.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>

src/intel/blorp/blorp.c

@@ -111,12 +111,7 @@ brw_blorp_surface_info_init(struct blorp_context *blorp,
       .format = format,
       .base_level = level,
       .levels = 1,
-      .channel_select = {
-         ISL_CHANNEL_SELECT_RED,
-         ISL_CHANNEL_SELECT_GREEN,
-         ISL_CHANNEL_SELECT_BLUE,
-         ISL_CHANNEL_SELECT_ALPHA,
-      },
+      .swizzle = ISL_SWIZZLE_IDENTITY,
    };
 
    info->view.array_len = MAX2(info->surf.logical_level0_px.depth,