radv/gfx9: use correct swizzle parameter to work out border swizzle.

This should fix:
dEQP-VK.pipeline.sampler.view_type.*.format.b4g4r4a4_unorm_pack16.address_modes.all_mode_clamp_to_border_opaque_black
and a few others in that area.

Fixes: b11c4a55 (radv: add texture descriptor/fmask/cmask support for GFX9)
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Signed-off-by: Dave Airlie <airlied@redhat.com>
(cherry picked from commit a4c23ce1)