drm/msm: Avoid rounding down to zero jiffies

If userspace asked for a timeout greater than zero, but less than a
jiffy, they clearly weren't planning on spinning. So it is better
to round up to one.

This fixes an issue with supertuxkart that was (for some reason)
spinning on a gl sync with 1ms timeout. CPU time for a demo lap
drops from:

15.83user 20.98system 0:47.46elapsed 77%CPU

drops to:

8.84user 2.30system 0:46.67elapsed 23%CPU

Signed-off-by: Rob Clark <[e-mail]>
Reviewed-by: Dmitry Baryshkov <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/528725/
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Baryshkov <[e-mail]>

drivers/gpu/drm/msm/msm_drv.h

···
 		remaining_jiffies = ktime_divns(rem, NSEC_PER_SEC / HZ);
 	}
 
-	return clamp(remaining_jiffies, 0LL, (s64)INT_MAX);
+	return clamp(remaining_jiffies, 1LL, (s64)INT_MAX);
 }
 
 /* Driver helpers */