[ALSA] ice1724: fix MIDI

The VT1724 MIDI port is not MPU-401 compatible; remove the hacks that
try to make the MPU-401 library work with it, and just use some simple
device-specific code.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Tested-by: Pavel Hofman <pavel.hofman@insite.cz>