arm: armv7m: clean up armv7m unified code compilation

unified syntax should be selected by config ARM_ASM_UNIFIED

Signed-off-by: Vikas Manocha <vikas.manocha@st.com>
diff --git a/arch/arm/lib/crt0.S b/arch/arm/lib/crt0.S
index d7ff9f0..fe312db 100644
--- a/arch/arm/lib/crt0.S
+++ b/arch/arm/lib/crt0.S
@@ -8,9 +8,7 @@
 #include <config.h>
 #include <asm-offsets.h>
 #include <linux/linkage.h>
-#ifdef CONFIG_CPU_V7M
-#include <asm/armv7m.h>
-#endif
+#include <asm/assembler.h>
 
 /*
  * This file handles the target-independent stages of the U-Boot