scsi: ufs: enable ufs driver to support generic PHY framework

In this change, ufs driver is using the generic PHY framework,
by calling the API "devm_phy_get" that returns handle to a generic
PHY driver.

In this change "__maybe_unused" flag of a few callbacks is removed
since those callbacks are now hooked to generic PHY driver APIs that
were added.

This change also includes the required DT changes as in this case,
the driver changes derived from the DT changes and therefor must
be placed within the same change.

Change-Id: I10e15e25d050bedca55a058b79240360564aebcd
Signed-off-by: Yaniv Gardi <ygardi@codeaurora.org>