ALSA: memalloc: Revive x86-specific WC page allocations again

We dropped the x86-specific hack for WC-page allocations with a hope
that the standard dma_alloc_wc() works nowadays.  Alas, it doesn't,
and we need to take back some workaround again, but in a different
form, as the previous one was broken for some platforms.

This patch re-introduces the x86-specific WC-page allocations, but it
uses rather the manual page allocations instead of
dma_alloc_coherent().  The use of dma_alloc_coherent() was also a
potential problem in the recent addition of the fallback allocation
for noncontig pages, and this patch eliminates both at once.

Fixes: 9882d63b ("ALSA: memalloc: Drop x86-specific hack for WC allocations")
Cc: <stable@vger.kernel.org>
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=216363
Link: https://lore.kernel.org/r/20220821155911.10715-1-tiwai@suse.de


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