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/gxbb/platform.mk b/plat/amlogic/gxbb/platform.mk
index 5ab4d52..e69f3f6 100644
--- a/plat/amlogic/gxbb/platform.mk
+++ b/plat/amlogic/gxbb/platform.mk
@@ -8,6 +8,7 @@
 
 AML_PLAT		:=	plat/amlogic
 AML_PLAT_SOC		:=	${AML_PLAT}/${PLAT}
+AML_PLAT_COMMON		:=	${AML_PLAT}/common
 
 PLAT_INCLUDES		:=	-I${AML_PLAT_SOC}/include
 
@@ -23,7 +24,7 @@
 
 BL31_SOURCES		+=	lib/cpus/aarch64/cortex_a53.S		\
 				plat/common/plat_psci_common.c		\
-				${AML_PLAT_SOC}/aarch64/gxbb_helpers.S	\
+				${AML_PLAT_COMMON}/aarch64/aml_helpers.S	\
 				${AML_PLAT_SOC}/gxbb_bl31_setup.c	\
 				${AML_PLAT_SOC}/gxbb_efuse.c		\
 				${AML_PLAT_SOC}/gxbb_mhu.c		\