hwc: Enable source split for targets with single dsi

Enable source split for targets with single dsi. This has the
benefit of using 2 pipes for layers whose width (crop) is higher
than line width.

Change-Id: I147136a3eb786e1af7b63508d65c010e88e358ed
overlay: Fix BWC buffer size

BWC buffer size was added to address worst case sizes. But it doesn't
take care of RGB formats. Also the YUV CbCr worst case is 32x2 not
64x2. This change fixes those.

Change-Id: I72277bc1858ce704b34c831a73ce8cbcd93925fa
hwc: Fix tearing with RGB layer rotation

Pass the acquire fence count to driver on a buffer sync ioctl call
for the rotator. The count is always 1 since the ioctl is called
once per rotator session. This also means that the rotator has to
wait for only 1 layer always.

The earlier assumption that in the presence of a session id, the
acquire count would be NOP, does not seem to hold with the driver.

Change-Id: I986a436194c66e8ce2a2afb363627f72dc6e20cd