wifi: mwifiex: Detach sync cmd buffer on interrupted wait

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

wifi: mwifiex: Detach sync cmd buffer on interrupted wait

mwifiex synchronous commands keep the caller-provided data buffer in
cmd_node->data_buf. Several callers pass stack-allocated objects there.

If wait_event_interruptible_timeout() is interrupted, the caller can
return and release that stack object while the firmware command is still
the current command. A late firmware response then reaches the normal
response handler, which can copy data through cmd_node->data_buf into the
stale stack address.

This fixes a stack corruption observed during repeated association and
disassociation cycles. The panic trace showed the command wait being
interrupted immediately before a bad pointer dereference:

cmd_wait_q terminated: -512
Unable to handle kernel paging request at virtual address 002c583837384662
Kernel panic - not syncing: stack-protector: Kernel stack is corrupted
...
Tainted: [M]=MACHINE_CHECK

The fault address decodes as little-endian ASCII:

0x002c583837384662 -> "bF878X,\0"

which is a fragment of the VERSION_EXT firmware string exposed as
debugfs "verext":

w8997o-V4, RF878X, FP92, 16.92.21.p153.7

The same runs also showed corrupted control data containing:

0x2400372e333531 -> "153.7\0$"

which is the tail of the same VERSION_EXT string. This points at a late
VERSION_EXT response writing through a stale stack-backed data_buf after
the interrupted wait returned.

After cancelling pending commands on an interrupted or timed-out wait,
detach the caller-owned data buffer from the still-current command. This
preserves the existing command cancellation behaviour while preventing a
late response from writing through a pointer whose lifetime ended with the
waiting caller.

Tested on an i.MX8MP board using an 88W8997.