power: pmic: sunxi: use generic AXP SPL driver for AXP313

The generic AXP SPL driver implementation can cover all regulators we
need for the AXP313.

Add the descriptions for the three DC/DC regulators of the AXP313, and
enable that when CONFIG_AXP313_POWER is enabled. Also remove the old
driver, and switch the Makefile to include the new, generic version.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
3 files changed