iio: adc: exynos: Simplify Exynos7-specific init

The Exynos7-specific code bits in ADC driver do not play with PHY:
the field exynos_adc_data.needs_adc_phy is not set in exynos7_adc_data
instance.  Therefore the initialization code does not have to check if
it is true.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Tested-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>