staging: rtl8723bs: Delete file odm_AntDiv.c

Delete file odm_AntDiv.c and corresponding header file odm_AntDiv.h as
its functions and definitions are not used anywhere.
Remove reference to odm_AntDiv.h.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>