phy: samsung: ufs: support secondary ufs phy

To support secondary ufs phy device, we need to get an offset for phy
isolation from the syscon DT node. If the first index argument of the
node is existing, we can read the offset value and set it as isol->offset.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Link: https://lore.kernel.org/r/20220607072907.127000-6-chanho61.park@samsung.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>