qseecom: use of_reserved_mem_lookup to get heap base and size

As cma_get_base and cma_get_size are not intended to be used by
leaf drivers on GKI enabled build, use of_reserved_mem_lookup to
get heap base and size.

Change-Id: I91194187c89ff8c7f7d445833afce1a4716f0ea4
Signed-off-by: Zhen Kong <zkong@codeaurora.org>