msm: mhi_dev: UCI memory leak fix

mhi_init_read_chan() allocates max_packet_size*nr_trbs for async client for
inbound channel. Multiple open/close of channels can cause memory leak.
Adding free operation during channel release to resolve this.

Change-Id: I7be4d47d28140a4d04b5070cb7db776a7f909238
Signed-off-by: Subramanian Ananthanarayanan <skananth@codeaurora.org>
Signed-off-by: Gauri Joshi <gaurjosh@codeaurora.org>