anv/blorp: Don't sanitize the swizzle for blorp_clear

anv/blorp: Don't sanitize the swizzle for blorp_clear

BLORP is now smart enough to handle any swizzle (even those that contain
ZERO or ONE) in a reasonable manner.  Just let BLORP handle it.  This
fixes the following Vulkan CTS tests on Haswell:

 - dEQP-VK.api.image_clearing.clear_color_image.1d_b4g4r4a4_unorm_pack16
 - dEQP-VK.api.image_clearing.clear_color_image.2d_b4g4r4a4_unorm_pack16
 - dEQP-VK.api.image_clearing.clear_color_image.3d_b4g4r4a4_unorm_pack16

Reviewed-by: Juan A. Suarez Romero <jasuarez@igalia.com>
Cc: "17.0" <mesa-stable@lists.freedesktop.org>