trivial: fix an -> a typos in documentation and comments

It is always "an" if there is a vowel _spoken_ (not written).
So it is:
"an hour" (spoken vowel)
but
"a uniform" (spoken 'j')

Signed-off-by: Frederik Schwarzer <schwarzerf@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/misc/phantom.c b/drivers/misc/phantom.c
index abdebe3..fa57b67 100644
--- a/drivers/misc/phantom.c
+++ b/drivers/misc/phantom.c
@@ -6,7 +6,7 @@
  *  the Free Software Foundation; either version 2 of the License, or
  *  (at your option) any later version.
  *
- *  You need an userspace library to cooperate with this driver. It (and other
+ *  You need a userspace library to cooperate with this driver. It (and other
  *  info) may be obtained here:
  *  http://www.fi.muni.cz/~xslaby/phantom.html
  *  or alternatively, you might use OpenHaptics provided by Sensable.