ARM: multi_v7_defconfig: Add STM32F7 I2C & STM32 USBPHYC support

This patch adds STM32F7 I2C support to multi_v7_defconfig and
enable the STM32 USB PHY Controller (USBPHYC) driver, implemented on
STM32MP1 SoC.

Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Amelie Delaunay <amelie.delaunay@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>
Signed-off-by: Olof Johansson <olof@lixom.net>