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.