ALSA: emu10k1: fix faulty commit 18c71092

Commit 18c71092

 had #endif leftoff from
compilation. This patch fixes it.
Also, I replaced a misplaced comment by a useful one, that explains why are
here #ifdef and #endif added in compilation.

Signed-off-by: Vedran Miletic <rivanvx@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>