power: Tidy up #undef of CONFIG_DM_PMIC

power: Tidy up #undef of CONFIG_DM_PMIC

Add a proper Kconfig option for SPL so we can remove the hack in some of
the board config files.

This involves adding CONFIG_SPL_DM_PMIC to some of the configs as well
as updateing the Makefile rule for PMIC_RK8XX to exclude SPL.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
[trini: Add SPL_PMIC_RK8XX, enable when needed, handle undef of
        CONFIG_DM_PMIC_PFUZE100 as well]
Signed-off-by: Tom Rini <trini@konsulko.com>