dts: Kconfig: Fix help for SPL_OF_CONTROL

As initially this feature was implemented as a negative CONFIG and
later it was redesigned to be positive the help text should be
updated to reflect this change.

This commit updates the help text to match the current implementation.

Signed-off-by: Walter Lozano <wlozano@collabora.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed