Since b904eca92f we depend on syscon once the "fsl,anatop" property is
found. select MFD_SYSCON to make sure it is available.

Fixes: b904eca92f ("usb: imx-usb-phy: Disable charger detect during initialization")
Cc: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>