Revert "of/fdt: Make sure no-map does not remove already reserved regions"

This reverts commit 3cbd3038.
It is not really a fix, and the backport misses dependencies, which
breaks existing platforms.

Reported-by: Alexandre TORGUE <alexandre.torgue@foss.st.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>