ALSA: sgio2audio: Remove usage of dropped hw_params/hw_free functions

Commit ee88f4eb ("ALSA: mips: Use managed buffer allocation") removed
superfluous hw_params/hw_free callbacks, but forgot to remove them where
they were used.

Fixes: ee88f4eb

 ("ALSA: mips: Use managed buffer allocation")
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Link: https://lore.kernel.org/r/20200306105837.31523-1-tsbogend@alpha.franken.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>