ALSA: memalloc: Use DMA API for x86 WC page allocations, too

ALSA: memalloc: Use DMA API for x86 WC page allocations, too

The memalloc helper used a house-made code for allocation of WC pages
on x86, since the standard DMA API doesn't cover it well.  Meanwhile,
the manually allocated pages won't work together with IOMMU, resulting
in faults, so we should switch to the DMA API in that case, instead.

This patch tries to switch back to DMA API for WC pages on x86, but
with some additional tweaks that are missing.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=219087
Link: https://patch.msgid.link/20240801064808.31205-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>