drm/i915/gt: Increase suspend timeout

With GuC submission on DG1, the execution of the requests times out
for the gem_exec_suspend igt test case after executing around 800-900
of 1000 submitted requests.

Given the time we allow elsewhere for fences to signal (in the order of
seconds), increase the timeout before we mark the gt wedged and proceed.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Acked-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210922062527.865433-4-thomas.hellstrom@linux.intel.com