ath10k: Release some resources in an error handling path

Should an error occur after calling 'ath10k_usb_create()', it should be
undone by a corresponding 'ath10k_usb_destroy()' call

Fixes: 4db66499

 ("ath10k: add initial USB support")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20201122170358.1346065-1-christophe.jaillet@wanadoo.fr