ALSA: asihpi - DSP code loader API now independent of OS

The loader API has been revised so that OS specific data is kept
local to hpidspcd.c, and the public API is unchanged across OSes.

Signed-off-by: Eliot Blennerhassett <eblennerhassett@audioscience.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>