Fix unterminated literal in Makefile

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Merge branch 'master' of http://github.org/lwfinger/rtl8723au_bt
rtl8723au_bt: Fix to build on all kernels

The API changed at kernel 3.13.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>