ARM: dts: msm: Add l2pc-cpu-mask to avoid L2PC on masked CPUs for msm8998

This is required to add a PM QOS request to disallow L2PC on masked CPUS.
It improves queue to submit time for first set of GPU commands
which results in GPU wake up.

Change-Id: If7e0925ec76065158188671f1d11a0de5e9900aa
Signed-off-by: Gaurav Sonwani <gsonwani@codeaurora.org>