msm: kgsl: fix paren placement leading to fence timeout

The incorrect paren placement can lead to a fence timeout
because the last_timestamp is always written. As a result
the last_timestamp could be corrupted by writing an old
value leading to a future timestamp_cmp indicating that a
signaled sync pt was unsignaled.

Change-Id: I4650a467bfdd98a905f86fbec7d833596c67ba19
Signed-off-by: Jeff Boody <jboody@codeaurora.org>