ALSA: hda - Allow different ops to read/write registers

The forthcoming platform hda driver needs to override the way
registers are read and written.  In preparation for that, introduce a
reg_ops struct that can be implemented differently by the new driver.
Change the existing macros to use the new structure, and move them to
hda_priv.h where they will be accessible to both PCI and platform
drivers.

Start with register access, but later commits will add more ops that
differ between PCI and platform.

Signed-off-by: Dylan Reid <dgreid@chromium.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>