Introduce a new option --extra-space instead of using IMAGE_EXTRA_SPACE.
This is useful for boot partitions where the extra space is often
useless or for huge partition where 10MiB may not be enough.
Change-Id: I13036e434f06b8f56b6951bd7583d91e3404e070 Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com> Signed-off-by: Ross Burton <ross.burton@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org> Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
