Remove ASM_ASSERTION check in Makefile

ASM_ASSERTION was deprecated long ago, this check is no longer needed.

Change-Id: I2a5770f76ea1317461c0059dad8dba9dc0e5af32
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Makefile

@@ -26,10 +26,6 @@ include ${MAKE_HELPERS_DIRECTORY}build_env.mk
 # Default values for build configurations, and their dependencies
 ################################################################################
 
-ifdef ASM_ASSERTION
-        $(warning ASM_ASSERTION is removed, use ENABLE_ASSERTIONS instead.)
-endif
-
 include ${MAKE_HELPERS_DIRECTORY}defaults.mk
 
 # Assertions enabled for DEBUG builds by default