power: supply: ab8500_fg: drop duplicated 'is' in comment

Fix word duplication typo 'is is' -> 'is'.
Signed-off-by: Jiang Jian <jiangjian@cdjrlc.com>
[update commit message]
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/ab8500_fg.c

@@ -412,7 +412,7 @@ static int ab8500_fg_add_cap_sample(struct ab8500_fg *di, int sample)
  * ab8500_fg_clear_cap_samples() - Clear average filter
  * @di:		pointer to the ab8500_fg structure
  *
- * The capacity filter is is reset to zero.
+ * The capacity filter is reset to zero.
  */
 static void ab8500_fg_clear_cap_samples(struct ab8500_fg *di)
 {