ALSA: x86: Use standard mmap helper for Intel HDMI LPE audio

Intel HDMI LPE audio driver has its own mmap callback that mimics with
the noncached page attributes, but this is rather superfluous and can
be replaced with the standard helper, as the device is only for
playback and the write-cache should suffice.

This patch drops the own code and just uses the standard helper.

Link: https://lore.kernel.org/r/20220305083308.15718-1-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>