WIP: RFC: lg-hammerhead: increase CMA and VRAM

This helps to avoid plasmashell crashes with the following errors in dmesg:

[  217.689040] msm fd900000.mdss: [drm:get_pages] *ERROR* could not get pages: -28

I'm certainly not sure about how big those numbers should be. I only know that increasing only CMA size does not help, increasing msm.vram is mandatory.

Longer explanation: -28 is errno for ENOSPC which kernel memory allocation function somewhere in msm_gem.c returns when it cannot find a contiguous block of memory large enough for a given request (?). Ideally nothing in user-space should crash horribly in that case, but..

Any thoughts and ideas welcome

cc @z3ntu @masneyb maybe