usb: gadget: f_midi: fail if set_alt fails to allocate requests

usb: gadget: f_midi: fail if set_alt fails to allocate requests

commit f0f1b8cac4d8d973e95f25d9ea132775fb43c5f4 upstream.

This ensures that the midi function will only work if the proper number of
IN and OUT requrests are allocated. Otherwise the function will work with less
requests then what the user wants.

Signed-off-by: Felipe F. Tonello <eu@felipetonello.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
From: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>