drirc: Set glsl_zero_init for Kerbal Space Program.

drirc: Set glsl_zero_init for Kerbal Space Program.

This fixes the stripes of garbage rendered on the floor of the vehicle
assembly building among other rendering issues.  The reason for the
misrendering seems to be that some of the GLSL shaders used by the
application use variables before initializing them, incorrectly
assuming that they will be implicitly set to zero by the
implementation.

Acked-by: Matt Turner <mattst88@gmail.com>