powerpc/85xx: Make eSDHC 1-bit only transfer mode default for MPC8569E-MDS

For yet unknown reason 4-bit mode doesn't work on MPC8569E-MDS boards,
so make 1-bit mode default. When we resolve the issue, u-boot will
remove sdhci,1-bit-only property from the device tree, while SDHCI
will still work with older u-boots.
Signed-off-by: NAnton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>

arch/powerpc/boot/dts/mpc8569mds.dts

@@ -253,6 +253,7 @@
 			/* Filled in by U-Boot */
 			clock-frequency = <0>;
 			status = "disabled";
+			sdhci,1-bit-only;
 		};
 
 		crypto@30000 {