clk: qcom: clk-rpmh: remove xo_board clock as parent

Defining xo_board as parent of RPMh clocks causes them to
become orphaned. Remove this clock as parent.

Change-Id: I31edf592de28a5f7f52f18917a09a862de510a6f
Signed-off-by: Osvaldo Banuelos <osvaldob@codeaurora.org>