arm: mvebu: ac5: Define mvebu_get_nand_clock()

The NF_CLK for the AC5 SoC runs at 400MHz. There's no strapping
or gating require so just add a mvebu_get_nand_clock() that
returns this value.

Signed-off-by: Chris Packham <judge.packham@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>

arch/arm/mach-mvebu/alleycat5/soc.c

@@ -255,6 +255,12 @@ void soc_print_clock_info(void)
 	printf("\tMSS     %4d MHz\n", 200);
 }
 
+/* Return NAND clock in Hz */
+u32 mvebu_get_nand_clock(void)
+{
+	return 400 * 1000000;
+}
+
 /*
  * Override of __weak int mach_cpu_init(void) :
  * SoC/machine dependent CPU setup