Remove CONFIG_IS_ENABLED() macro in the driver, it seems the macro don't work
in the config build for mx6sxsabreauto_config platform.

And CONFIG_IS_ENABLED(FOO) evaluates to
 *  1 if CONFIG_SPL_BUILD is undefined and CONFIG_FOO is set to 'y' or 'm',
 *  1 if CONFIG_SPL_BUILD is defined and CONFIG_SPL_FOO is set to 'y' or 'm'

If enable CONFIG_SPL_BUILD, then CONFIG_FOO doesn't work.

Now remove the CONFIG_IS_ENABLED() in the driver.

Signed-off-by: Fugang Duan <fugang.duan@nxp.com>