sunxi: Convert CONFIG_MACPWR to Kconfig

Convert the CONFIG_MACPWR to Kconfig and update all the sunxi defconfigs
that used it in SYS_EXTRA_OPTIONS.

Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>