of: move definition of of_chosen into common code.

Rather than defining of_chosen in each arch, it can be defined for all
in driver/of/base.c

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/kernel/prom.c

@@ -42,9 +42,6 @@
 #include <asm/sections.h>
 #include <asm/pci-bridge.h>
 
-/* export that to outside world */
-struct device_node *of_chosen;
-
 void __init early_init_dt_scan_chosen_arch(unsigned long node)
 {
 	/* No Microblaze specific code here */