drm/amdkfd: Clear MODE.VSKIP in gfx9 trap handler

If user shader issues S_SETVSKIP then this state will persist when
executing the trap handler, causing vector instructions to be
skipped.

VSKIP state is already saved/restored through the MODE register.

Signed-off-by: Jay Cornwall <[email protected]>
Reviewed-by: Lancelot Six <[email protected]>
Suggested-by: Alex Deucher <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>

Author: jcornwallAMD