power:pmic: Rename ./drivers/power/pmic_* to ./drivers/power/power_* files

Rename pmic/power related files at ./drivers/power directory

Signed-off-by: Lukasz Majewski <l.majewski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Stefano Babic <sbabic@denx.de>