arm64: zynqmp: Propagate error value from psu_init()

psu_init() returns int which wasn't declared and checked.
The patch is fixing function declarations and code to handle return
values properly.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/arm/include/asm/arch-zynqmp/sys_proto.h

@@ -33,7 +33,7 @@ enum {
 int zynq_board_read_rom_ethaddr(unsigned char *ethaddr);
 unsigned int zynqmp_get_silicon_version(void);
 
-void psu_init(void);
+int psu_init(void);
 
 void handoff_setup(void);