efi_loader: create reservations after ft_board_setup

Some memory reservations are made in ft_board_setup(). Ensure that we
create reserved memory map entries after ft_board_setup().

The downside of this patch is that if bootefi is called multiple times with
an devicetree argument superfluous reservations for the old copies of the
device tree will exist. But that is still better than missing a reservation.

Deleting the superfluous reservations is not possible because reservations
in the memory map are rounded to page size and may be coallesced.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>