Some drivers using of_register_platform_driver() wrapper break on sparc
because the wrapper isn't in the header file.  This patch moves it from
Microblaze and PowerPC implementations and makes it common code.

Fixes this sparc64 allmodconfig build error (at least):

drivers/leds/leds-gpio.c: In function `gpio_led_init':
drivers/leds/leds-gpio.c:295: error: implicit declaration of function `of_register_platform_driver'
drivers/leds/leds-gpio.c: In function `gpio_led_exit':
drivers/leds/leds-gpio.c:311: error: implicit declaration of function `of_unregister_platform_driver'
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>