ARM: meson: rework soc arch file to prepare for new SoC

We are about to add support for the Amlogic AXG SoC. While very close to
the Gx SoC family, we will need to handle a few thing which are different
in this SoC. Rework the meson arch directory to prepare for this.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
diff --git a/arch/arm/mach-meson/Kconfig b/arch/arm/mach-meson/Kconfig
index 6f60167..6225417 100644
--- a/arch/arm/mach-meson/Kconfig
+++ b/arch/arm/mach-meson/Kconfig
@@ -8,25 +8,29 @@
 	select DM_SERIAL
 	imply CMD_DM
 
+config MESON_GX
+	bool
+	select MESON64_COMMON
+
 choice
 	prompt "Platform select"
 	default MESON_GXBB
 
 config MESON_GXBB
 	bool "GXBB"
-	select MESON64_COMMON
+	select MESON_GX
 	help
 	  Select this if your SoC is an S905
 
 config MESON_GXL
 	bool "GXL"
-	select MESON64_COMMON
+	select MESON_GX
 	help
 	  Select this if your SoC is an S905X/D or S805X
 
 config MESON_GXM
 	bool "GXM"
-	select MESON64_COMMON
+	select MESON_GX
 	help
 	  Select this if your SoC is an S912