drm/i915/selftests: Follow up on increase timeout in i915_gem_contexts selftests

Follow up on below commit, to increase the timeout further on new
platforms, to accomodate the additional time required for the completion
of guc submissions for numerous requests created in loop.

commit 5e076529
Author: Matthew Brost <matthew.brost@intel.com>
Date:   Mon Jul 26 20:17:03 2021 -0700

    drm/i915/selftests: Increase timeout in i915_gem_contexts selftests

Signed-off-by: Bruce Chang <yu.bruce.chang@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211207003845.12419-1-yu.bruce.chang@intel.com