test: test the ESRT creation

test: test the ESRT creation

This commit slightly extends test_efi_capsule_fw3.

 In order to run the test the following must be added to
 sandbox_defconfig:
  +CONFIG_CMD_SF=y
  +CONFIG_CMD_MEMORY=y
  +CONFIG_CMD_FAT=y
  +CONFIG_DFU=y

 The ESRT is printed in the u-boot shell by calling efidebug esrt.
 The test ensures that, after the capsule is installed, the  ESRT
 contains entries with the GUIDs:
  - EFI_FIRMWARE_IMAGE_TYPE_UBOOT_FIT_GUID;
  - EFI_FIRMWARE_IMAGE_TYPE_UBOOT_RAW_GUID;

test invocation:
 sudo ./test/py/test.py --bd sandbox -k capsule_fw3 -l --build

CC: Heinrich Schuchardt	<xypron.glpk@gmx.de>
CC: Sughosh Ganu <sughosh.ganu@linaro.org>
CC: AKASHI Takahiro <takahiro.akashi@linaro.org>
CC: Ilias Apalodimas <ilias.apalodimas@linaro.org>
CC: Andre Przywara <andre.przywara@arm.com>
CC: Alexander Graf <agraf@csgraf.de>
CC: nd@arm.com
Signed-off-by: Jose Marinho <jose.marinho@arm.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>