shader_runner: Remove unsigned comparison against 0.

ux has type unsigned.

Fix defect reported by Coverity Scan.

Unsigned compared against 0 (NO_EFFECT) unsigned_compare: This less-than-zero comparison of an unsigned value is never true. ux < 0U.

Fixes: 728dde0e ("shader_runner: add xfb testing support") Signed-off-by: Vinson Lee vlee@freedesktop.org