comedi: Fix memory leak in compat_insnlist()

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

comedi: Fix memory leak in compat_insnlist()

`compat_insnlist()` handles the 32-bit version of the `COMEDI_INSNLIST`

ioctl (whenwhen `CONFIG_COMPAT` is enabled). It allocates memory to

temporarily hold an array of `struct comedi_insn` converted from the

32-bit version in user space. This memory is only being freed if there

is a fault while filling the array, otherwise it is leaked.

Add a call to `kfree()` to fix the leak.