USB: serial: kobil_sct: fix modem-status error handling

USB: serial: kobil_sct: fix modem-status error handling

[ Upstream commit a420b5d939ee58f1d950f0ea782834056520aeaa ]

Make sure to return -EIO in case of a short modem-status read request.

While at it, split the debug message to not include the (zeroed)
transfer-buffer content in case of errors.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>