USB: update MAINAINERS and CREDITS for Freescale USB driver

Add MAINAINERS and CREDITS entry for Freescale Highspeed USB device
driver.

Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>