n/kms: fix num_banks tiling config for fusion

The field is encoded:
0 = 4 banks
1 = 8 banks
2 = 16 banks

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
bCŠÞ’Sx