arm: armv7m: Clean up some thumb / compiler flag options

- The correct way to build with thumb mode is to select SYS_THUMB_BUILD
- We should be setting -march=armv7-m in arch/arm/Makefile not the
  sub-config.mk file.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index d273294..0d1802b 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -221,6 +221,7 @@
 	select THUMB2_KERNEL
 	select SYS_CACHE_SHIFT_5
 	select SYS_ARM_MPU
+	select SYS_THUMB_BUILD
 
 config CPU_V7R
 	bool
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 4d6d276..680c6e8 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -16,6 +16,7 @@
 arch-$(CONFIG_CPU_ARM1176)	=-march=armv5t
 arch-$(CONFIG_CPU_V7A)		=$(call cc-option, -march=armv7-a, \
 				 $(call cc-option, -march=armv7, -march=armv5))
+arch-$(CONFIG_CPU_V7M)		=-march=armv7-m
 arch-$(CONFIG_CPU_V7R)		=-march=armv7-r
 arch-$(CONFIG_ARM64)		=-march=armv8-a
 
diff --git a/arch/arm/cpu/armv7m/config.mk b/arch/arm/cpu/armv7m/config.mk
index 4e46df5..f50964c 100644
--- a/arch/arm/cpu/armv7m/config.mk
+++ b/arch/arm/cpu/armv7m/config.mk
@@ -3,4 +3,4 @@
 # (C) Copyright 2015
 # Kamil Lulko, <kamil.lulko@gmail.com>
 
-PLATFORM_CPPFLAGS += -march=armv7-m -mthumb -mno-unaligned-access
+PLATFORM_CPPFLAGS += -mno-unaligned-access