cmd: load: add load command for memory mapped

cp.b is used a lot as a way to load binaries to memory and execute
them, however we may need to integrate this with the efi subsystem to
set it up as a bootdev.

So, introduce a loadm command that will be consistent with the other
loadX commands and will call the efi API's.

ex: loadm $kernel_addr $kernel_addr_r $kernel_size

with this a kernel with CONFIG_EFI_STUB enabled will be loaded and
then subsequently booted with bootefi command.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/README b/README
index 9800359..f330422 100644
--- a/README
+++ b/README
@@ -2415,6 +2415,7 @@
 diskboot- boot from IDE devicebootd   - boot default, i.e., run 'bootcmd'
 loads	- load S-Record file over serial line
 loadb	- load binary file over serial line (kermit mode)
+loadm   - load binary blob from source address to destination address
 md	- memory display
 mm	- memory modify (auto-incrementing)
 nm	- memory modify (constant address)