snow: use bootblock build class for GPIO

This gets rid of a bunch of copy + pasted GPIO code.

Change-Id: I548b2b5d63642a9da185eb7b34f80cbebf9b124f
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: http://review.coreboot.org/2288
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/cpu/samsung/exynos5250/Makefile.inc

@@ -8,6 +8,7 @@
 # in the bootblock and try moving it entirely into romstage.
 bootblock-y += clock_init.c
 bootblock-y += clock.c
+bootblock-y += pinmux.c
 bootblock-y += soc.c
 bootblock-y += uart.c
 

src/cpu/samsung/s5p-common/Makefile.inc

@@ -1,4 +1,5 @@
 bootblock-y += pwm.c
+bootblock-y += s5p_gpio.c
 bootblock-y += timer.c
 
 romstage-y += cpu_info.c