imx: mx7: avoid some initialization if low level is skipped

We can have the case where u-boot is launched after some other low level
enabler, like for example when u-boot runs after arm-trusted-firmware
and/or optee. So, because of that we may need to jump the initialization of
some IP blocks even because we may no longer have the permission for that.

So, if the config option to skip low level init is set disable also timer,
board and csu initialization.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: u-boot@lists.denx.de
Reviewed-by: Peng Fan <peng.fan@nxp.com>