imx: Move some i.MX common functions into the imx-common directory

This patch moves the following functions into the imx-common
directory:

- mxs_wait_mask_set()
- mxs_wait_mask_clr()
- mxs_reset_block()

These are currently used by i.MX28. But the upcoming GPMI NAND port
for i.MX6 will also use these functions. So lets move them to a
common location to re-use them.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
diff --git a/Makefile b/Makefile
index 84b0c43..d1d286b 100644
--- a/Makefile
+++ b/Makefile
@@ -331,7 +331,7 @@
 LIBS-y += $(CPUDIR)/omap-common/libomap-common.o
 endif
 
-ifneq (,$(filter $(SOC), mx25 mx27 mx5 mx6 mx31 mx35))
+ifneq (,$(filter $(SOC), mx25 mx27 mx5 mx6 mx31 mx35 mxs))
 LIBS-y += arch/$(ARCH)/imx-common/libimx-common.o
 endif