phy: qcom-snps: Add a set mode callback

The set mode handler is used to keep track of the current role of the
device.  This is used for enabling certain resources within the PHY
depending on if the device is behaving as a host or device.

Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
Link: https://lore.kernel.org/r/20200625195444.15130-3-wcheng@codeaurora.org


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