firmware: xilinx: Remove PM_API_MAX value

There is no reason to keep PM_API_MAX around. The commit acfdd185
("firmware: xilinx: Use hash-table for api feature check") removed its
usage that's why it is not used anywhere now.
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/86e94593a29a1b5b1958c539a1bfabdd08c0948e.1610959734.git.michal.simek@xilinx.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/firmware/xlnx-zynqmp.h

@@ -85,7 +85,6 @@ enum pm_api_id {
 	PM_CLOCK_GETPARENT,
 	PM_SECURE_AES = 47,
 	PM_FEATURE_CHECK = 63,
-	PM_API_MAX,
 };
 
 /* PMU-FW return status codes */