csky: Cast argument to virt_to_pfn() to (void *)

The virt_to_pfn() function takes a (void *) as argument, fix
this up to avoid exploiting the unintended polymorphism of
virt_to_pfn.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>

arch/arc/include/asm/page.h

@@ -108,7 +108,7 @@ extern int pfn_valid(unsigned long pfn);
 
 #else /* CONFIG_HIGHMEM */
 
-#define ARCH_PFN_OFFSET		virt_to_pfn(CONFIG_LINUX_RAM_BASE)
+#define ARCH_PFN_OFFSET		virt_to_pfn((void *)CONFIG_LINUX_RAM_BASE)
 
 #endif /* CONFIG_HIGHMEM */