staging: gpib: Add local include file for commands

Add the functions and enums needed only by the kernel drivers
that were removed from the uapi/gpib.h include file to a separate
local include file.

Include this new file in the gpibP.h local include file.

Signed-off-by: Dave Penkler <dpenkler@gmail.com>
Link: https://lore.kernel.org/r/20250603184320.30594-3-dpenkler@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>