staging: gpib: Use __user for user space pointers

The user buffers in copy_from_user, copy_to_user and some file ops
did not use the __user address space attribute.

This led to the following sparse warning, for example:
common/gpib_os.c:838:40: warning: incorrect type in argument 2 (different address spaces)
common/gpib_os.c:838:40:    expected void const [noderef] __user *from
common/gpib_os.c:838:40:    got void *

Add the __user address space attribute where needed.

Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Link: https://lore.kernel.org/r/20250114165403.16410-3-dpenkler@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: dpenkler