ARM: shmobile: r8a7791: add MMCIF max-frequency

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7791.dtsi

@@ -494,6 +494,7 @@
 		dma-names = "tx", "rx";
 		reg-io-width = <4>;
 		status = "disabled";
+		max-frequency = <97500000>;
 	};
 
 	sdhi0: sd@ee100000 {