drm/msm/sde: all bw calculations for wb/virtual display

This change adds the BW calculation for WB and virtual display,
without this change if WB is used after primary display
is suspended the WB operation is executed at XO clock and
without bandwidth vote leading to timeouts.

Change-Id: I1174e6042dedc21a229bd4526cf0b3848399bdd7
Signed-off-by: Narendra Muppalla <NarendraM@codeaurora.org>