MAINTAINERS: Add STM32MP1 RNG driver in stm32mp platform

Add the STM32MP1 RNG driver in the list of drivers supported by
the STMicroelectronics STM32MP15x series.
Signed-off-by: NPatrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: NPatrice Chotard <patrice.chotard@st.com>

MAINTAINERS

@@ -430,6 +430,7 @@ F:	drivers/power/regulator/stpmic1.c
 F:	drivers/ram/stm32mp1/
 F:	drivers/remoteproc/stm32_copro.c
 F:	drivers/reset/stm32-reset.c
+F:	drivers/rng/stm32mp1_rng.c
 F:	drivers/rtc/stm32_rtc.c
 F:	drivers/serial/serial_stm32.*
 F:	drivers/spi/stm32_qspi.c