arm: exynos: Use proper PMIC device names

Since commit 4213609c ("drivers: core: use strcmp when find device by
name") one has to provide full name to get requested object. Fix the code
used to detect enable power regulators on the supported Exynos boards to
use proper PMIC device device name then.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Anand Moon <linux.amoon@gmail.com>
Reviewed-by: Lukasz Majewski <lukma@denx.de>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>