drm/amdkfd: Fix gfx9 XNACK state save/restore

SQ_WAVE_IB_STS.RCNT grew from 4 bits to 5 in gfx9. Do not truncate
when saving in the high bits of TTMP1.

Signed-off-by: Jay Cornwall <Jay.Cornwall@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>