Enforce correct -march option

Buildroot uses a normal ARM compiler to build the AM33X CM3 firmware
(which runs on a Cortex-M3 processor), but Buildroot will have a
default -march value that doesn't necessarily match the one needed for
Cortex-M3, leading to build failures (gcc complains that the
-mcpu=cortex-m3 option being passed is not compatible with the
selected -march).

Fix this by explicitly indicating -march=armv7-m.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Updated the patch to the latest version of the Makefile

Signed-off-by: Anders Darander <anders@chargestorm.se>

Index: b/Makefile
===================================================================
--- a/Makefile
+++ b/Makefile
@@ -13,7 +13,7 @@ SRCDIR = src
 BINDIR = bin
 
 INCLUDES = $(SRCDIR)/include
-CFLAGS =-mcpu=cortex-m3 -mthumb -nostdlib -Wall -Wundef \
+CFLAGS =-march=armv7-m -mcpu=cortex-m3 -mthumb -nostdlib -Wall -Wundef \
 	-Werror-implicit-function-declaration -Wstrict-prototypes \
 	-Wdeclaration-after-statement -fno-delete-null-pointer-checks \
 	-Wempty-body -fno-strict-overflow  -g -I$(INCLUDES) -O2