EFI: fix error handling in efi_get_boot() ...

efi_get_global_var() returns an error code, not NULL when it fails.

Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

EFI: introduce efi_strguid to convert GUID to human readable names ...

use in devinfo Protocols

Tested today on qemu with all the GUID translated

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Add initial EFI architecture support ...

This adds support for running barebox in an EFI environment
on X86 PC hardware.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>