msm: kgsl: Correctly check for room in context queue

Currently, _wait_for_room_in_context_queue checks space for a single
draw object. This can lead to buffer overflow if multiple drawobjects
are submitted. Fix this by checking space for appropriate number
of draw objects.

Change-Id: I9144d7eebf0f93fe438e15606efc70eb42746d7e
Signed-off-by: Kamal Agrawal <kamaagra@codeaurora.org>