msm: kgsl: Use temp unsigned long variable to prevent truncation

Casting the output of adreno_wait_event_interruptible_timeout() to
int can cause problems on 64bit since msecs_to_jiffies() returns an
unsigned long. This results in ret having negative values which are
not appropriately handled. Instead, use a temp variable to get the
returned value and translate that into a return value.

Change-Id: I5d1d2b40b4b832bdb018560630ab77dce98ea866
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>