usb: gadget: use config_ep_by_speed() instead of ep_choose()

Remove obsolete functions:
1. ep_choose()
2. usb_find_endpoint()

Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
[idos@codeaurora.org: Changed also the following files to
comply with this commit: f_accessory.c,f_adb.c,f_diag.c,f_mtp.c,
f_rmnet.c,f_rmnet_sdio,f_rmnet_smd,f_rmnet_smd_sdio,f_serial.f_ccid.c.
Also merged a patch in f_serial.c for checking return value of
config_ep_by_speed, see "usb: gadget: fix g_serial regression".
Also fix a bug in ci13xxx_udc. Since f_serial is now checking if the endpoint
descriptors are null in the set_alt function, need to set them to null on
ep_disable in case of cable disconnect. Since the ep descriptor was inserted to
struct usb_ep in "usb: gadget: add usb_endpoint_descriptor to struct usb_ep",
also set mEp->ep.desc to NULL. I have upstream this to the community, please
see "usb: gadget: Clear usb_endpoint_descriptor inside the struct usb_ep" in
the latest linux kernel.]
Signed-off-by: Ido Shayevitz <idos@codeaurora.org>