softpipe: Silence warning about uninitialized variable
src/gallium/auxiliary/tgsi/tgsi_exec.c:3098:48: Warning: »interp« could be used uninitialised [-Wmaybe-uninitialized] mach->InputSampleOffsetApply[i] = interp;
src/gallium/auxiliary/tgsi/tgsi_exec.c:3098:48: Warning: »interp« could be used uninitialised [-Wmaybe-uninitialized] mach->InputSampleOffsetApply[i] = interp;