staging: rtl8723bs: move function prototypes out of os_dep/int_fs.c

staging: rtl8723bs: move function prototypes out of os_dep/int_fs.c

fix the following checkpatch issues:

WARNING: externs should be avoided in .c files
196: FILE: drivers/staging/rtl8723bs/os_dep/os_intfs.c:196:
+int _netdev_open(struct net_device *pnetdev);
--
WARNING: externs should be avoided in .c files
197: FILE: drivers/staging/rtl8723bs/os_dep/os_intfs.c:197:
+int netdev_open(struct net_device *pnetdev);

moved function prototype in include/osdep_intf.h
removed function prototype and made a static
removed unnecessary extern declaration in os_dep/ioctl_cfg80211.c

Signed-off-by: Fabio Aiuto <fabioaiuto83@gmail.com>
Link: https://lore.kernel.org/r/4604b856b9c20f1141e19894f46934cb860eebd4.1616503354.git.fabioaiuto83@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>