staging: gpib: Add missing mutex unlock in ni usb driver

staging: gpib: Add missing mutex unlock in ni usb driver

When the buffer allocation for return data in ni_usb_write() fails
we were returning without unlocking the addressed_transfer_lock.

Add the unlock call.

This was detected by smatch:
New smatch warnings:
drivers/staging/gpib/ni_usb/ni_usb_gpib.c:837 ni_usb_write() warn: inconsistent returns '&ni_priv->addressed_transfer_lock'.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202412201550.9NCO57Ye-lkp@intel.com/
Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Link: https://lore.kernel.org/r/20250111161548.27601-1-dpenkler@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>