[ARM] MXC: add cpu_is_ macros

We had hardcoded cpu_is_ macros for mxc architectures till now. As we
want to run the same kernel on i.MX31 and i.MX35 this patch adds cpu_is_
macros which expand to 0 or 1 if only one architecture is compiled in and
only check for the cpu type if more than one architecture is compiled
in.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
diff --git a/arch/arm/mach-mx3/clock.c b/arch/arm/mach-mx3/clock.c
index bc3a3be..9ab5f8b 100644
--- a/arch/arm/mach-mx3/clock.c
+++ b/arch/arm/mach-mx3/clock.c
@@ -1077,6 +1077,8 @@
 	u32 reg;
 	struct clk **clkp;
 
+	mxc_set_cpu_type(MXC_CPU_MX31);
+
 	ckih_rate = fref;
 
 	for (clkp = mxc_clks; clkp < mxc_clks + ARRAY_SIZE(mxc_clks); clkp++)