We have a special handling of WC pages on x86, and it's currently
specific to HD-audio. The last forgotten piece was the pgprot setup
for the mmap with WC pages.
This patch moves the pgprot setup for WC pages from HD-audio-specific
mmap callback to the common helper code. It allows us to remove the
superfluous mmap callback in HD-audio and its prepare_mmap
redirection.
Link: https://lore.kernel.org/r/20210804061329.29265-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>