ARM: multi_v7_defconfig: Enable st ohci and ehci HCD drivers.

Enable the ehci and ohci drivers in the multi_v7_defconfig so that
the USB controllers on stih41x work by default.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>