USB: g_mass_storage: fix section mismatch warnings

The recent commit (0e530b45) that moved usb_ep_autoconfig from the
__devinit section to the __init section missed the mass storage device.
Its fsg_bind() function uses the usb_ep_autoconfig() function from non
__init context leading to:
WARNING: drivers/usb/gadget/g_mass_storage.o(.text): Section mismatch in
	reference from the function _fsg_bind()
	            to the function .init.text:_usb_ep_autoconfig()

So move fsg_bind() into __init as well.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>