msm: kgsl: use kvmalloc for ringbuffer submission

kmalloc returns out of memory in low memory conditions even if memory
is available in non-contiguous manner. This results in failure to
submit commands to ringbuffer. Use kvmalloc in place of kmalloc so
that when kmalloc fails in low memory conditions, commands can be
submitted if vmalloc can provide enough memory.

Change-Id: If6a20e35983982b5c0888e5f7dabecfa8c026bcb
Signed-off-by: Pranav Patel <quic_pranavp@quicinc.com>