cmd: bootefi: Parse reserved-memory node from DT

Currently, bootefi only parses memory reservation block to setup
EFI reserved memory mappings. However, it doesn't parse the
reserved-memory[1] device tree node that also can contain the
reserved memory regions.

Add capability to parse reserved-memory node and update the EFI memory
mappings accordingly.

1. <U-Boot source>/doc/device-tree-bindings/reserved-memory/reserved-memory.txt]

Signed-off-by: Atish Patra <atish.patra@wdc.com>

Fix an endless loop.

The /reserved-memory node may have children without reg property. Remove
a superfluous debug statement.

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