The i.MX6 Quad SoC will work without the l2x0 L2 cache controller
support built into the kernel, so this patch removes the dependency
on CACHE_L2X0.

This makes the l2x0 support optional, so that it can be turned off
when desired for debugging purposes etc.

Since SOC_IMX6Q already depends on ARCH_IMX_V6_V7 and
ARCH_IMX_V6_V7 selects MIGHT_HAVE_CACHE_L2X0, there is no need to
select that option explicitly from SOC_IMX6Q.

Thanks to Shawn Guo for this suggestion.  [1]

[1] http://lists.infradead.org/pipermail/linux-arm-kernel/2011-November/074602.htmlAcked-by: NShawn Guo <shawn.guo@linaro.org>
Tested-by: NShawn Guo <shawn.guo@linaro.org>
Acked-by: NSascha Hauer <s.hauer@pengutronix.de>