wlcore, wl1251: fix spelling: "Couldnt" -> "Couldn't" and remove error on -ENOMEM

Trivial fix to spelling mistake in error message text.  Also remove the
error message on an kzalloc failure as this is redundant.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>