imximage.cfg: run files through C preprocessor

The '#' used as comments in the files cause the preprocessor
trouble, so change to /* */.

The mkimage command which uses this preprocessor output
was moved to arch/arm/imx-common/Makefile

.gitignore was updated to ignore .cfgtmp files.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
diff --git a/arch/arm/cpu/armv7/config.mk b/arch/arm/cpu/armv7/config.mk
index 9c3e2f3..350e946 100644
--- a/arch/arm/cpu/armv7/config.mk
+++ b/arch/arm/cpu/armv7/config.mk
@@ -40,5 +40,5 @@
 PLATFORM_NO_UNALIGNED := $(PF_NO_UNALIGNED)
 
 ifneq ($(CONFIG_IMX_CONFIG),)
-ALL-y	+= $(obj)u-boot.imx
+ALL-y	+= $(OBJTREE)/u-boot.imx
 endif