V4L/DVB: cx18-alsa: name alsa device after the actual card

Use the cx18 board name in the ALSA description, to make it easier for users
who run "arecord -l" to see which device they should be looking for.

Also, use strlcpy() instead of strcpy().

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>