ARM: versatile: mark mmc_status() static

mmc_status() is only used in the file it is defined in, and
no longer has an 'extern' declaration:

arch/arm/mach-versatile/versatile.c:56:14: error: no previous prototype for 'mmc_status'

Fixes: 16956fed ("ARM: versatile: switch to DT only booting and remove legacy code")
Link: https://lore.kernel.org/r/20230516153109.514251-14-arnd@kernel.orgSigned-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/mach-versatile/versatile.c

@@ -53,7 +53,7 @@
 
 static void __iomem *versatile_sys_base;
 
-unsigned int mmc_status(struct device *dev)
+static unsigned int mmc_status(struct device *dev)
 {
 	struct amba_device *adev = container_of(dev, struct amba_device, dev);
 	u32 mask;