pvr: Support clear colours with more than 32 bits
The support for this already exists, but was blocked by a conditional. Replace with an assert to ensure the format can be packed into 4x32 bit words (true for all currently supported formats).
Signed-off-by: Matt Coster <matt.coster@imgtec.com>
Reviewed-by: Frank Binns <frank.binns@imgtec.com>
Edited by Matt Coster