BACKPORT: kgsl: hwsched: Don't cross dereference kgsl_mem_entry pointer

The passed in pointer in kgsl_count_hw_fences() can be a
kgsl_mem_entry pointer. This gets cross dereferenced to
a kgsl_drawobj_sync_event pointer and causes a NULL pointer
dereference. To avoid this cross dereference, decouple the two
paths and call kgsl_count_hw_fences() only in the appropriate
path.

Change-Id: I1088a0b67f1f82a20ddc94c94cbdd31a44b18da6
Signed-off-by: Harshdeep Dhatt <quic_hdhatt@quicinc.com>