amlogic: Move assembly helpers to common directory

The assembly helpers are common to all the amlogic SoCs. Move the .S
file to the common directory.

Signed-off-by: Carlo Caione <ccaione@baylibre.com>
Change-Id: I0d8616a7ae22dbcb14848cefd0149b6bb5814ea6
diff --git a/plat/amlogic/gxl/platform.mk b/plat/amlogic/gxl/platform.mk
index 41a6261..f699381 100644
--- a/plat/amlogic/gxl/platform.mk
+++ b/plat/amlogic/gxl/platform.mk
@@ -8,6 +8,7 @@
 
 AML_PLAT		:=	plat/amlogic
 AML_PLAT_SOC		:=	${AML_PLAT}/${PLAT}
+AML_PLAT_COMMON		:=	${AML_PLAT}/common
 
 DOIMAGEPATH		?=	tools/amlogic
 DOIMAGETOOL		?=	${DOIMAGEPATH}/doimage
@@ -28,7 +29,7 @@
 
 BL31_SOURCES		+=	lib/cpus/aarch64/cortex_a53.S		\
 				plat/common/plat_psci_common.c		\
-				${AML_PLAT_SOC}/aarch64/gxl_helpers.S	\
+				${AML_PLAT_COMMON}/aarch64/aml_helpers.S	\
 				${AML_PLAT_SOC}/gxl_bl31_setup.c	\
 				${AML_PLAT_SOC}/gxl_efuse.c		\
 				${AML_PLAT_SOC}/gxl_mhu.c		\