ath10k: Improve grammar in comments

Signed-off-by: Geert Uytterhoeven <geert+renesas@linux-m68k.org>
Cc: John W. Linville <linville@tuxdriver.com>
Cc: linux-wireless@vger.kernel.org
Signed-off-by: Jiri Kosina <jkosina@suse.cz>