target: rename cortex_m3.[ch] to cortex_m.[ch]

This rename is in preparation for cortex_m4 support.

Change-Id: Ic08c298ec6ed2aabc2c39db67191f68b3a51f550
Signed-off-by: Spencer Oliver <spen@spen-soft.co.uk>
Reviewed-on: http://openocd.zylin.com/147
Tested-by: jenkins
Reviewed-by: Øyvind Harboe <oyvindharboe@gmail.com>

src/target/Makefile.am

@@ -73,7 +73,7 @@ ARMV6_SRC = \
 
 ARMV7_SRC = \
 	armv7m.c \
-	cortex_m3.c \
+	cortex_m.c \
 	armv7a.c \
 	cortex_a.c
 
@@ -137,7 +137,7 @@ noinst_HEADERS = \
 	dsp563xx_once.h \
 	dsp5680xx.h \
 	breakpoints.h \
-	cortex_m3.h \
+	cortex_m.h \
 	cortex_a.h \
 	embeddedice.h \
 	etb.h \