MAINTAINERS: Add maintainer entry for the imx8 DDR PMU driver

Frank Li wrote the imx8 DDR PMU driver and has access to the hardware,
so add him as maintainer for the files in question.
Signed-off-by: NFrank Li <Frank.Li@nxp.com>
[will: fixed case of title]
Signed-off-by: NWill Deacon <will.deacon@arm.com>

MAINTAINERS

@@ -6328,6 +6328,13 @@ L:	linux-i2c@vger.kernel.org
 S:	Maintained
 F:	drivers/i2c/busses/i2c-cpm.c
 
+FREESCALE IMX DDR PMU DRIVER
+M:	Frank Li <Frank.li@nxp.com>
+L:	linux-arm-kernel@lists.infradead.org
+S:	Maintained
+F:	drivers/perf/fsl_imx8_ddr_perf.c
+F:	Documentation/devicetree/bindings/perf/fsl-imx-ddr.txt
+
 FREESCALE IMX LPI2C DRIVER
 M:	Dong Aisheng <aisheng.dong@nxp.com>
 L:	linux-i2c@vger.kernel.org