MAINTAINERS: Add ehci-st.c and ohci-st.c to ARCH/STI architecture

This patch adds the ehci-st.c and ohci-st.c files for the usb 2.0
& usb1.1 host controller drivers found on stih41x and stih4xx STMicroelectronics
SoC's into the STI arch section of the maintainers file.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>