drm/radeon/cik: Fix encoding of number of banks in tiling configuration info

There are multiple valid values, not just 0 or 1.  Required
to properly support 2D tiling in the userspace drivers.

Cc: stable@vger.kernel.org
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>