arm64: versal: Define zynqmp_mmio_write() for versal

GQSPI driver is using it but this function is never called for Versal
because it is removed by linker. But function should be declared to avoid
this build warning:
drivers/spi/zynqmp_gqspi.c: In function 'zynqmp_qspi_set_tapdelay':
drivers/spi/zynqmp_gqspi.c:378:3: warning: implicit declaration of function
'zynqmp_mmio_write' [-Wimplicit-function-declaration]
  378 |   zynqmp_mmio_write(IOU_TAPDLY_BYPASS_OFST,

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma@amd.com>
Link: https://lore.kernel.org/r/20220825125906.11581-3-ashok.reddy.soma@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com>
diff --git a/arch/arm/mach-versal/include/mach/sys_proto.h b/arch/arm/mach-versal/include/mach/sys_proto.h
index 05934c2..8e5712e 100644
--- a/arch/arm/mach-versal/include/mach/sys_proto.h
+++ b/arch/arm/mach-versal/include/mach/sys_proto.h
@@ -3,6 +3,8 @@
  * Copyright 2016 - 2018 Xilinx, Inc.
  */
 
+#include <linux/build_bug.h>
+
 enum {
 	TCM_LOCK,
 	TCM_SPLIT,
@@ -10,3 +12,9 @@
 
 void tcm_init(u8 mode);
 void mem_map_fill(void);
+
+static inline int zynqmp_mmio_write(const u32 address, const u32 mask, const u32 value)
+{
+	BUILD_BUG();
+	return -EINVAL;
+}