dri2: reply to client for WaitMSC request in any case

otherwise client would wait for reply forever and desktop appears hang.

Signed-off-by: Flora Cui <flora.cui@amd.com>
Acked-by: Feifei Xu <Feifei.Xu@amd.com>
12 jobs for master in 1 minute and 21 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Docker Image
passed #342474
debian-testing

00:00:26

 
  Build
passed #342477
xserver-1.13

00:00:33

passed #342478
xserver-1.14

00:00:52

passed #342479
xserver-1.15

00:00:54

passed #342480
xserver-1.16

00:00:42

passed #342481
xserver-1.17

00:00:47

passed #342482
xserver-1.18

00:00:44

passed #342483
xserver-1.18-clang

00:00:48

passed #342484
xserver-1.19

00:00:46

passed #342485
xserver-1.19-clang

00:00:49

passed #342475
xserver-1.20

00:00:54

passed #342476
xserver-1.20-clang

00:00:36