phy: qcom-ufs: parse ref-clk details prior to resource request

Do not request a resource if the ref clk regulator details are
not defined in ufs phy node.

Change-Id: I10eb426d4407388681340cb71fe9e761794dc298
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
[cang@codeaurora.org: resolved trivial merge conflicts
and fixed kernel compilation error by removing returning
no error if optional is ture]
Signed-off-by: Can Guo <cang@codeaurora.org>