scsi: ufs: ufs-qcom: Add support for finding HS gear on new UFS versions

Starting from UFS controller v4, Qcom supports dual gear mode (i.e., the
controller/PHY can be configured to run in two gear speeds). But that
requires an agreement between the UFS controller and the UFS device.
This commit finds the max gear supported by both controller and device
then decides which one to use.

UFS controller's max gear can be read from the REG_UFS_PARAM0 register and
UFS device's max gear can be read from the "max-device-gear" devicetree
property.

The UFS PHY also needs to be configured with the decided gear using the
phy_set_mode_ext() API.

Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Andrew Halaney <ahalaney@redhat.com>