rtlwifi: Modify core.c for new drivers

Each of the routines in the rtlwifi common driver needs to be modified
for the coming changes. This patch prepares core.c, but also touches other
files.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>