ALSA: rme9652: Hardening for potential Spectre v1

ALSA: rme9652: Hardening for potential Spectre v1

commit f526afcd8f71945c23ce581d7864ace93de8a4f7 upstream.

As recently Smatch suggested, one place in RME9652 driver may expand
the array directly from the user-space value with speculation:
  sound/pci/rme9652/rme9652.c:2074 snd_rme9652_channel_info() warn: potential spectre issue 'rme9652->channel_map' (local cap)

This patch puts array_index_nospec() for hardening against it.

BugLink: https://marc.info/?l=linux-kernel&m=152411496503418&w=2
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>