drm/vblank: Use abs64(diff_ns) for s64 diff_ns instead of abs(diff_ns)
drm/vblank: Use abs64(diff_ns) for s64 diff_ns instead of abs(diff_ns)

Use of abs() wrongly wrapped diff_ns to 32 bit, which gives a 1/4000
probability of a missed vblank increment at each vblank irq reenable
if the kms driver doesn't support high precision vblank timestamping.
Not a big deal in practice, but let's make it nice.

Signed-off-by: Mario Kleiner <72d071d150c24522961f76cddfa9e5d9130c5153@tuebingen.mpg.de>
Signed-off-by: Dave Airlie <f2295d84e358395675bc8031be58672073ae065e@redhat.com>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas