efi_driver: create a parent device for all EFI block devices

Up to now root has been the parent device for all block devices created via
calling ConnectController(). This does not work well together with the
implementation of bootstd.

Add a dummy parent device for all EFI block devices.

With this change EFI block devices are also accessible via commands like
'cat', 'load', and 'ls'.

    => dm tree
     Class     Seq    Probed  Driver                Name
    -----------------------------------------------------------
     efi           0  [ + ]   EFI block driver      `-- efi
     blk           3  [ + ]   efi_blk                   `-- efi.efiblk#0
     partition     0  [ + ]   blk_partition                 `-- efi.efiblk#0:1

    => ls efiloader 0:1
           13   hello.txt
            7   u-boot.txt
    2 file(s), 0 dir(s)

    => cat efiloader 0:1 hello.txt
    Hello world!

    => efidebug dh
    0000000018df1700 (efi.efiblk#0:1)
      /VenHw(dbca4c98-6cb0-694d-0872-819c650cb7b8)/HD(1,MBR,0xd1535d21,0x1,0x7f)
      Block IO
      Simple File System

Adjust the event dump unit test to consider the new event spy.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/test/py/tests/test_event_dump.py b/test/py/tests/test_event_dump.py
index 45143c1..177b982 100644
--- a/test/py/tests/test_event_dump.py
+++ b/test/py/tests/test_event_dump.py
@@ -19,6 +19,7 @@
 EVT_FT_FIXUP          bootmeth_vbe_ft_fixup           .*boot/vbe_request.c:.*
 EVT_FT_FIXUP          bootmeth_vbe_simple_ft_fixup    .*boot/vbe_simple_os.c:.*
 EVT_LAST_STAGE_INIT   alloc_write_acpi_tables         .*lib/acpi/acpi_table.c:.*
+EVT_LAST_STAGE_INIT   efi_block_device_create         .*lib/efi_driver/efi_block_device.c:.*
 EVT_LAST_STAGE_INIT   install_smbios_table            .*lib/efi_loader/efi_smbios.c:.*
 EVT_MISC_INIT_F       sandbox_early_getopt_check      .*arch/sandbox/cpu/start.c:.*
 EVT_TEST              h_adder_simple                  .*test/common/event.c:'''