msm: kgsl: Ignore signals for ringbuffer timestamp waits

Ignore signals when waiting for ringbuffer timestamp since
the wait needs to complete regardless of whether the process
got a signal. Also, increase the wait timeout for context
detachment to 30s instead of 10s. Large IB's can take longer
than 10s to retire and if a hang happens then recovering from
the hang and completing the long IB's will take much longer
than 10s, bump this timer to 30s which should be sufficient
for the context's commands to retire even if hang happens.

Change-Id: I54589c9ec48da3f87ccc60c85451daac7e9a22bd
CRs-Fixed: 718284
Signed-off-by: Shubhraprakash Das <sadas@codeaurora.org>