[ALSA] timer: check for incorrect device state in non-debug compiles, too

Convert the snd_assert()s to simple if()s to prevent crashes when one of
the timer instance ioctls is called before the file is bound to a timer
device.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>