arch: Make phys_initrd_start and phys_initrd_size global variables

Make phys_initrd_start and phys_initrd_size global variables declared in
init/do_mounts_initrd.c such that we can later have generic code in
drivers/of/fdt.c populate those variables for us.

This requires both the ARM and unicore32 implementations to be properly
guarded against CONFIG_BLK_DEV_INITRD, and also initialize the variables
to the expected default values (unicore32).

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 32e4845..4386257 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -50,9 +50,7 @@ unsigned long __init __clear_cr(unsigned long mask)
 }
 #endif
 
-static phys_addr_t phys_initrd_start __initdata = 0;
-static unsigned long phys_initrd_size __initdata = 0;
-
+#ifdef CONFIG_BLK_DEV_INITRD
 static int __init early_initrd(char *p)
 {
 	phys_addr_t start;
@@ -89,6 +87,7 @@ static int __init parse_tag_initrd2(const struct tag *tag)
 }
 
 __tagtable(ATAG_INITRD2, parse_tag_initrd2);
+#endif
 
 static void __init find_limits(unsigned long *min, unsigned long *max_low,
 			       unsigned long *max_high)