ARM: imx: temporarily remove CONFIG_SOC_FSL from LS1021A

The newly introduced LS1021A SoC selects CONFIG_SOC_FSL, which
is originally symbol used for the PowerPC based platforms
and guards lots of code that does not build on ARM.

This breaks allmodconfig, so let's remove it for now, until
either all those drivers are fixed or they use a dependency
on IMX instead.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>