MAINTAINERS: Add ahci_st.c to ARCH/STI architecture

This patch adds the ahci_st.c driver found on STMicroelectronics
stih41x consumer electronics 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>
Acked-by: Maxime Coquelin <maxime.coquelin@st.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

MAINTAINERS

@@ -1422,6 +1422,7 @@ F:	drivers/tty/serial/st-asc.c
 F:	drivers/usb/dwc3/dwc3-st.c
 F:	drivers/usb/host/ehci-st.c
 F:	drivers/usb/host/ohci-st.c
+F:	drivers/ata/ahci_st.c
 
 ARM/TECHNOLOGIC SYSTEMS TS7250 MACHINE SUPPORT
 M:	Lennert Buytenhek <kernel@wantstofly.org>