mwifiex: fix spelling mistake "capabilties" -> "capabilities"

There various spelling mistakes in function names and in message
text. Fix these.

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