bus: mhi: host: Drop chan lock before queuing buffers

In the Linux kernel, the following vulnerability has been resolved: bus: mhi: host: Drop chan lock before queuing buffers Ensure read and write locks for the channel are not taken in succession by dropping the read lock from parse_xfer_event() such that a callback given to client can potentially queue buffers and acquire the write lock in that process. Any queueing of buffers should be done without channel read lock acquired as it can result in multiple locks and a soft lockup. [mani: added fixes tag and cc'ed stable]