ARM: dts: msm: Increase SMP block restriction for 8x26

Change SMP block allocation per pipe restriction from 2 to 4.
This avoids underruns observed in few usecases on targets
having high resolution panels like 1200p.

Change-Id: Id439ea711617da2292e8d7c388766b6cbda1b89d
Signed-off-by: Mayank Chopra <makchopra@codeaurora.org>