[PATCH] mfd: mc13xxx: add I2C support fix building for v3.4

You ask me about another solution?

quoted

I'm saying either I'm missing something or this needs to be fixed in the
patches that introduce the regmap usage.

You understood correctly, it took me time to understand :-)
No problem I can split this patch:

quoted

+     select REGMAP_I2C if I2C
+     select REGMAP_SPI if SPI_MASTER

It will go to  v4 mfd: mc13xxx-core: use regmap for register access, 

Only the second part will be in this patch

-	struct device_node *np = mc13xxx->dev.of_node;
+	struct device_node *np = mc13xxx->dev->of_node;