msm: kgsl: Re-define maximum number of cmds for hwscheduling

HFI messages are only SZ_1K bytes. From this, derive HWSCHED_MAX_NUMIBS
as the number of maximum IBs that can be in a single submission in
hwscheduling.

Change-Id: Id6d5cd2c8130479bc83f731ddd564af8c552e531
Signed-off-by: Harshdeep Dhatt <hdhatt@codeaurora.org>