ARM: dts: Restrict SMP buffer to 2

Motorola 8226s are 720p devices, so underruns should not happen at 2.

Squash of the following commits:

Revert "ARM: dts: msm: Tune SMP block restriction for 8x26"

This reverts commit 55901aba00d67d5c1947b2774ddd1098357f0626.

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

This reverts commit f8fe718ce8e108edcdbaf0f4257ac3caed0a267f.

Change-Id: I8488c99a57a42efc00e6f720b89c521ffc2756c8

Conflicts:
	arch/arm/boot/dts/msm8226-mdss.dtsi