Fix typos in Documentation/: 'S'

This patch fixes typos in various Documentation txts. The patch addresses
some words starting with the letter 'S'.

Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com>
Acked-by: Alan Cox <alan@redhat.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/Documentation/sound/alsa/MIXART.txt b/Documentation/sound/alsa/MIXART.txt
index 9fa5bbd..ef42c44 100644
--- a/Documentation/sound/alsa/MIXART.txt
+++ b/Documentation/sound/alsa/MIXART.txt
@@ -39,7 +39,7 @@
 substreams performing hardware mixing. This could be changed to a
 maximum of 24 substreams if wished.
 Mono files will be played on the left and right channel. Each channel
-can be muted for each stream to use 8 analog/digital outputs seperately.
+can be muted for each stream to use 8 analog/digital outputs separately.
 
 Capture
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