parport: gsc: mark init function static

This is only used locally, so mark it static to avoid a warning:

drivers/parport/parport_gsc.c:395:5: error: no previous prototype for 'parport_gsc_init' [-Werror=missing-prototypes]

Acked-by: Helge Deller <deller@gmx.de>
Acked-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Helge Deller <deller@gmx.de>