power: pm8921-charger: Add delay after turning on D0 (TCXO) clock

On APQ8064, TCXO cannot be turned off before its warm-up period (4ms).
This is not required on the platform which have a CXO. Add a warm-up
delay after turning on D0 (which turns on the TCXO).

Change-Id: I252372c35a9fdfaf4a9fade1594936b05c1b5745
Signed-off-by: Anirudh Ghayal <aghayal@codeaurora.org>