ALSA: fm801: convert rest outw() / inw() to use helpers

The patch introduces two new helpers fm801_iowrite16() and fm801_ioread16() to
write and read the registers by offset. Previously similar was done to access
the hardware registers by their names.

Signed-off-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>