usb: gadget: f_tcm: Fix some resource leaks in some error paths

If a memory allocation fails within a 'usb_ep_alloc_request()' call, the
already allocated memory must be released.

Fix a mix-up in the code and free the correct requests.

Fixes: c52661d6 ("usb-gadget: Initial merge of target module for UASP + BOT")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Felipe Balbi <balbi@kernel.org>