nitrogen6x: update kernel revision

Latest kernel from dizzy branch, will be part of daisy at some point.
Fixes support for the Nit6X_800x480 display.

Change-Id: I1a886998b3e3f12750bfc93f2d06f33047aa850f
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@theqtcompany.com>