ARM: dts: Switch max77686 regulators to GPIO control for exynos4412-trats2

Remove fixed regulators (duplicating what max77686 provides) and
add GPIO enable control to max77686 regulators.

This gives the system full control over those regulators. Previously
the state of such regulators was a mixture of what max77686 driver set
over I2C and what regulator-fixed set through GPIO.

Removal of 'regulator-always-on' from CAM_ISP_CORE_1.2V (buck9) allows
disabling it when it is not used. Previously this regulator was always
enabled because its enable state is a OR of:
 - ENB9 GPIO (turned always on by regulator-fixed),
 - BUCK9EN field in BUCK9CTRL register (off by max77686 through I2C).

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>