sunxi: axp: Move axp pmic register helpers to a separate file

Move the register helpers used to access the registers via p2wi resp.
rsb bus on the otherwise identical axp221 and axp223 pmics to a separate
file, so that they can be used by the upcoming standalone axp gpio driver
too.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
diff --git a/arch/arm/cpu/armv7/sunxi/Makefile b/arch/arm/cpu/armv7/sunxi/Makefile
index 3052b27..9a1eeec 100644
--- a/arch/arm/cpu/armv7/sunxi/Makefile
+++ b/arch/arm/cpu/armv7/sunxi/Makefile
@@ -27,6 +27,8 @@
 obj-$(CONFIG_MACH_SUN8I)	+= clock_sun6i.o
 obj-$(CONFIG_MACH_SUN9I)	+= clock_sun9i.o
 
+obj-$(CONFIG_AXP221_POWER)	+= pmic_bus.o
+
 ifndef CONFIG_SPL_BUILD
 ifdef CONFIG_ARMV7_PSCI
 obj-y	+= psci.o