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/cmd/Kconfig b/cmd/Kconfig
index 9a0b720..dea3729 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -1160,6 +1160,11 @@
 	help
 	  Load a binary file over serial line.
 
+config CMD_LOADM
+	bool "loadm"
+	help
+	  Load a binary over memory mapped.
+
 config CMD_LOADS
 	bool "loads"
 	default y