disp: msm: sde: set parent to xo for link clks while enterting suspend

Clk framework will cache current parent and skip subsequent
clk_set_parent calls if same parent is set. In case of deepsleep,
clk's parent is reset to xo clks for link clocks but framework
will still see cached parent and skip set_parent call.
To avoid this state, set parent to xo clock for link clocks,
before we enter suspend, so that framework and hw state are
in correct state, when we exit from deepsleep.

Change-Id: Ic7f70ec13497c70a8b4351ebfa49c0db98fc63ab
Signed-off-by: Venkata Prahlad Valluru <quic_vvalluru@quicinc.com>