ARM: uniphier: add missing static qualifier

This function is for local use in the file.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/arch/arm/mach-uniphier/boot-mode/boot-mode-proxstream2.c b/arch/arm/mach-uniphier/boot-mode/boot-mode-proxstream2.c
index de12953..3769ec5 100644
--- a/arch/arm/mach-uniphier/boot-mode/boot-mode-proxstream2.c
+++ b/arch/arm/mach-uniphier/boot-mode/boot-mode-proxstream2.c
@@ -46,7 +46,7 @@
 	{BOOT_DEVICE_NONE, "Reserved"},
 };
 
-int get_boot_mode_sel(void)
+static int get_boot_mode_sel(void)
 {
 	return (readl(SG_PINMON0) >> 1) & 0x1f;
 }