efi_loader: disk: iterate only over valid block devices

efi_loader: disk: iterate only over valid block devices

The efi_loader currently stops iterating over the available
block devices stopping at the first device that fails.
This may imply that no block device is found.

With the patch efi_loader only iterates over valid devices.

It is based on patch
06d592bf52f6 (dm: core: Add uclass_first/next_device_check())
which is currently in u-boot-dm.git.

For testing I used an odroid-c2 with a dts including
&sd_emmc_a {
	status = "okay";
};
This device does not exist on the board and cannot be initialized.

Without the patch:

=> bootefi hello
## Starting EFI application at 01000000 ...
WARNING: Invalid device tree, expect boot to fail
mmc_init: -95, time 1806
Found 0 disks
Hello, world!
## Application terminated, r = 0

With the patch:

=> bootefi hello
## Starting EFI application at 01000000 ...
WARNING: Invalid device tree, expect boot to fail
mmc_init: -95, time 1806
Scanning disk mmc@70000.blk...
Scanning disk mmc@72000.blk...
Card did not respond to voltage select!
mmc_init: -95, time 9
Scanning disk mmc@74000.blk...
Found 3 disks
Hello, world!
## Application terminated, r = 0

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Alexander Graf <agraf@suse.de>