gpib: Fix memory leak in ni_usb_init()

gpib: Fix memory leak in ni_usb_init()

In ni_usb_init(), if ni_usb_setup_init() fails, the function returns
-EFAULT without freeing the allocated writes buffer, leading to a
memory leak.

Additionally, ni_usb_setup_init() returns 0 on failure, which causes
ni_usb_init() to return -EFAULT, an inappropriate error code for this
situation.

Fix the leak by freeing writes in the error path. Modify
ni_usb_setup_init() to return -EINVAL on failure and propagate this
error code in ni_usb_init().

Fixes: 4e127de14fa7 ("staging: gpib: Add National Instruments USB GPIB driver")
Suggested-by: Greg KH <gregkh@linuxfoundation.org>
Suggested-by: Dave Penkler <dpenkler@gmail.com>
Co-developed-by: Jianhao Xu <jianhao.xu@seu.edu.cn>
Signed-off-by: Jianhao Xu <jianhao.xu@seu.edu.cn>
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
Link: https://patch.msgid.link/20251230034546.929452-1-zilin@seu.edu.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>