dt-bindings: ufs: Add UFS VCCQ's parent regulator

Add the UFS's VCCQ parent regulator information so that the
software can perform load voting on this regulator.

Change-Id: I0bdfa1b5d3116dcb5a5d6db33f070dd7671e387d
Signed-off-by: Nitin Rawat <nitirawa@codeaurora.org>