staging: rtl8723bs: moved function prototype out of core/rtw_ioctl_set.c and core/rtw_mlme.c

fix the following checkpatch issues:

WARNING: externs should be avoided in .c files
40: FILE: drivers/staging/rtl8723bs/core/rtw_ioctl_set.c:40:
+u8 rtw_do_join(struct adapter *padapter);

WARNING: externs should be avoided in .c files
15: FILE: drivers/staging/rtl8723bs/core/rtw_mlme.c:15:
+extern u8 rtw_do_join(struct adapter *padapter);

moved function prototype in include/rtw_ioctl_set.h

Signed-off-by: Fabio Aiuto <fabioaiuto83@gmail.com>
Link: https://lore.kernel.org/r/da654adf1295123adca07e3e5809e256dd4def69.1616503354.git.fabioaiuto83@gmail.com


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