ARM: i.MX: initialize l2x0 at early_init time

This can make the l2 cache work at early time which
will benefit the boot up time.

Tested on i.mx31pdk board, test result shows:

Before: arch_initcall(mxc_init_l2x0);

[    0.558755] console [ttymxc0] enabled

After: early_initcall(mxc_init_l2x0);

[    0.555716] console [ttymxc0] enabled
Signed-off-by: NJason Liu <jason.hui@linaro.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>

arch/arm/mach-imx/cache-l2x0.c

@@ -53,4 +53,4 @@ static int mxc_init_l2x0(void)
 
 	return 0;
 }
-arch_initcall(mxc_init_l2x0);
+early_initcall(mxc_init_l2x0);