refactor(build): merge march32/64 directives

Both march32-directive and march64-directive eventually generate the
same march option that will passed to compiler.

Merge this two separate directives to a common one as march-directive.

Change-Id: I220d2b782eb3b54e13ffd5b6a581d0e6da68756a
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
diff --git a/make_helpers/armv7-a-cpus.mk b/make_helpers/armv7-a-cpus.mk
index eec85cc..a8e9d50 100644
--- a/make_helpers/armv7-a-cpus.mk
+++ b/make_helpers/armv7-a-cpus.mk
@@ -15,9 +15,9 @@
 # armClang requires -march=armv7-a for all ARMv7 Cortex-A. To comply with
 # all, just drop -march and supply only -mcpu.
 
-# Platform can override march32-directive through MARCH32_DIRECTIVE
-ifdef MARCH32_DIRECTIVE
-march32-directive		:= $(MARCH32_DIRECTIVE)
+# Platform can override march-directive through MARCH_DIRECTIVE
+ifdef MARCH_DIRECTIVE
+march-directive		:= $(MARCH_DIRECTIVE)
 else
 march32-set-${ARM_CORTEX_A5}	:= -mcpu=cortex-a5
 march32-set-${ARM_CORTEX_A7}	:= -mcpu=cortex-a7
@@ -29,7 +29,7 @@
 
 # default to -march=armv7-a as target directive
 march32-set-yes			?= -march=armv7-a
-march32-directive		:= ${march32-set-yes} ${march32-neon-yes}
+march-directive		:= ${march32-set-yes} ${march32-neon-yes}
 endif
 
 # Platform may override these extension support directives: