MAINTAINERS: Add phy-miphy28lp.c and phy-miphy365x.c to ARCH/STI architecture

This patch adds the phy-miphy28lp.c and phy-miphy365x.c phy drivers found on
STMicroelectronics stih407 family SoC's into the STI arch section of the
maintainers file.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>