ppir_op_sign and ppir_op_ceil support
Support ppir_op_sign and ppir_op_ceil in ppir. ppir_op_ceil only requires a few enum entries, ppir_op_sign is a bit more complicated since the mali pp does not support that operation directly. The ppir_op_sign implementation follows what the offline shader compiler does with comparison operations followed by a sub. These operations improve ppir completeness and also help piglit coverage since some tests require them.