ALSA: memalloc: Drop x86-specific hack for WC allocations

The recent report for a crash on Haswell machines implied that the
x86-specific (rather hackish) implementation for write-cache memory
buffer allocation in ALSA core is buggy with the recent kernel in some
corner cases.  This patch drops the x86-specific implementation and
uses the standard dma_alloc_wc() & co generically for avoiding the bug
and also for simplification.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=216112
Cc: <stable@vger.kernel.org> # v5.18+
Link: https://lore.kernel.org/r/20220620073440.7514-1-tiwai@suse.de


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