imx6q: Remove unconditional dependency on l2x0 L2 cache support

imx6q: Remove unconditional dependency on l2x0 L2 cache support

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.html

Acked-by: Shawn Guo <shawn.guo@linaro.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>