staging: gpib: Make static, reduce fwd declarations

staging: gpib: Make static, reduce fwd declarations

A number of drivers were unnecessarily not declaring their entry
points as static.

Declare them as static.

In order to reduce the number of forward declarations the gpib
interface structure initializations have been moved to after the
code of the entry points that they use. This also makes the
structure of the drivers to be more consistent between them.

Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/20250122103859.25499-3-dpenkler@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>