msm: mdss: support NRT VBIF XIN clients

WB interfaces' fetch XIN clients are connected to
Non-RealTime(NRT) VBIF on certain MDSS hardware. DMA
line mode fetch is connected to RealTime(RT) VBIF
while block mode fetch is connected to NRT VBIF on
such hardware. This change upgrades the driver to
support such MDSS hardware with NRT VBIF by updating
respective register space. It also selects RT vs NRT
VBIF client for DMA pipe based on operation mode.

Change-Id: Ia1680c2748ec0c9ef521df010ecfbcec78f5114f
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>