staging:rtl8821ae:btcoexist: Fix non-ANSI sparse warnings

This patch fixes the sparse warning:
drivers/staging/rtl8821ae/btcoexist/halbtcoutsrc.c:1080:41: warning: non-ANSI function declaration of function
by adding void to the parameterless function.

Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>