USB: remove CONFIG_EXPERIMENTAL dependancies

As discussed at the kernel summit this year, CONFIG_EXPERIMENTAL means
nothing, so let's get rid of it.

Acked-by: Felipe Balbi <balbi@ti.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: David Herrmann <dh.herrmann@googlemail.com>
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Neil Zhang <zhangwm@marvell.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>