Blackfin: import gpio/portmux layer from Linux

The current pinmux handling has spread throughout Blackfin drivers and
board code and is getting hideous to maintain.  So import the gpio and
portmux layer from the Blackfin Linux code.  This should spur a serious
of cleanups across the Blackfin tree.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/arch/blackfin/cpu/Makefile b/arch/blackfin/cpu/Makefile
index 50c1eea..91797c7 100644
--- a/arch/blackfin/cpu/Makefile
+++ b/arch/blackfin/cpu/Makefile
@@ -19,6 +19,7 @@
 SOBJS    := interrupt.o cache.o
 COBJS-$(CONFIG_BOOTCOUNT_LIMIT) += bootcount.o
 COBJS-y  += cpu.o
+COBJS-y  += gpio.o
 COBJS-y  += interrupts.o
 COBJS-$(CONFIG_JTAG_CONSOLE) += jtag-console.o
 COBJS-y  += os_log.o