phy: qcom-ufs: Use devm sibling of kstrdup for regulator names

This helps us in avoiding any requirement for kfree() operation
to be called exclusively over the allocated string pointer.

Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org>
Reviewed-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>