As the standard buffer allocation helper supports WC pages now, we can
convert bcm driver to use that.  This allows us to remove lots of
superfluous code.
Acked-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210802072815.13551-7-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>