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 <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: dpenkler