phy: qcom-ufs: add ufs phy type selection

Currently both 14nm phy and 20nm phy are compiled and built into
the kernel, while only one type is actually present and used.
Add a choice selection to the kernel configuration to specify
which phy type shall be used.

Change-Id: I5608d32fb4815db15e91a970e53099762eabbddd
Signed-off-by: Gilad Broner <gbroner@codeaurora.org>