initrd: cast `initrd_start' to `void *'

commit fb6624ebd912e3d6907ca6490248e73368223da9 (initrd: Fix virtual/physical
mix-up in overwrite test) introduced the compiler warning below on mips,
as its virt_to_page() doesn't cast the passed address to unsigned long
internally, unlike on most other architectures:

init/main.c: In function `start_kernel':
init/main.c:633: warning: passing argument 1 of `virt_to_phys' makes pointer from integer without a cast
init/main.c:636: warning: passing argument 1 of `virt_to_phys' makes pointer from integer without a cast

For now, kill the warning by explicitly casting initrd_start to `void *', as
that's the type it should really be.

Reported-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

init/main.c

@@ -635,10 +635,11 @@ asmlinkage void __init start_kernel(void)
 
 #ifdef CONFIG_BLK_DEV_INITRD
 	if (initrd_start && !initrd_below_start_ok &&
-	    page_to_pfn(virt_to_page(initrd_start)) < min_low_pfn) {
+	    page_to_pfn(virt_to_page((void *)initrd_start)) < min_low_pfn) {
 		printk(KERN_CRIT "initrd overwritten (0x%08lx < 0x%08lx) - "
 		    "disabling it.\n",
-		    page_to_pfn(virt_to_page(initrd_start)), min_low_pfn);
+		    page_to_pfn(virt_to_page((void *)initrd_start)),
+		    min_low_pfn);
 		initrd_start = 0;
 	}
 #endif