arm64: zynqmp: Do not use hardcoded address in do_zynqmp_reboot()

multi_boot is already the part of csu_base structure that's why use it
directly instead of using register offset value.

Fixes: fc001432e5 ("arm64: zynqmp: Add u-boot command to boot into recovery image")
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/3e5c6ea426b81cc73b90e6425764e41a98deb2a6.1733735454.git.michal.simek@amd.com

arch/arm/mach-zynqmp/zynqmp.c

@@ -349,7 +349,7 @@ static int do_zynqmp_reboot(struct cmd_tbl *cmdtp, int flag,
 
 	multiboot = hextoul(argv[2], NULL);
 
-	ret = zynqmp_mmio_write(0xFFCA0010, 0xfff, multiboot);
+	ret = zynqmp_mmio_write((ulong)&csu_base->multi_boot, 0xfff, multiboot);
 	if (ret != 0) {
 		printf("Failed: mmio write\n");
 		return ret;