pan/mdg: Fix calculation of available work registers
Make the rmu variable signed; otherwise the MAX2 has no effect and work_count can end up being larger than 16. Fixes INSTR_OPERAND_FAULTs in SuperTuxKart. Closes: #4707 Fixes: c6ed8bf7 ("panfrost: Fix uniform_count on Midgard") Reviewed-by:Boris Brezillon <boris.brezillon@collabora.com> Part-of: <!10507>