bus: mhi: core: Validate channel ID when processing command completions

In the Linux kernel, the following vulnerability has been resolved:

bus: mhi: core: Validate channel ID when processing command completions

MHI reads the channel ID from the event ring element sent by the

device which can be any value between 0 and 255. In order to

prevent any out of bound accesses, add a check against the maximum

number of channels supported by the controller and those channels

not configured yet so as to skip processing of that event ring

element.