ARM: sunxi: Make CPUCFG_BASE register macro sun7i specific

CPUCFG registers found at 0x01c25c00 is specific to sun7i,
so change the macro name to show it.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
ARM: sunxi: Make PSCI code sun7i specific

The PSCI code only works for sun7i. Rename it with _sun7i suffix,
and build only if building for sun7i.

This paves the way for adding PSCI support for other platforms.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
ARM: sunxi: Add sun6i specific CPUCFG register

The CPUCFG registers on sun6i are found in the RTC block
address range. Add a macro for it.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
ARM: sunxi: Add sun6i specific PSCI implementation

This adds PSCI support for sun6i. So far it only supports
the PWR_ON method.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
ARM: sunxi: Enable PSCI for sun6i

Now that we have a PSCI backend for sun6i, enable it.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>