brcmsmac: increase timer reference count for new timers only

commit a1fe52801a992e590cdaee2fb47a94bac9b5da90 upstream.

On hardware reintialization reference count of
already existing timers would be increased again.
This leads to problems on module unloading.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Piotr Haber <phaber@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>