USB: ehci-mxc: remove Efika MX-specific CHRGVBUS hack

Since Efika MX platform support (pre-devicetree) was removed from the tree
this code no longer has any possibility of running and clutters up the
driver which is being replaced by the chipidea host in the future anyway.

Signed-off-by: Matt Sealey <matt@genesi-usa.com>
Tested-by: Steev Klimazewski <steev@genesi-usa.com>
CC: Sascha Hauer <kernel@pengutronix.de>
CC: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>