efi_selftest: enable CONFIG_CMD_POWEROFF

For automating testing we should be able to power off the test system.
The implementation of EFI_RESET_SHUTDOWN requires the do_poweroff()
function which is only available if CONFIG_CMD_POWEROFF=y.

Enable CONFIG_CMD_POWEROFF if PSCI reset is available.
Signed-off-by: NHeinrich Schuchardt <xypron.glpk@gmx.de>

lib/efi_selftest/Kconfig

@@ -3,6 +3,7 @@ config CMD_BOOTEFI_SELFTEST
 	depends on CMD_BOOTEFI
 	imply FAT
 	imply FAT_WRITE
+	imply CMD_POWEROFF if PSCI_RESET || SYSRESET_PSCI
 	help
 	  This adds a UEFI test application to U-Boot that can be executed
 	  via the 'bootefi selftest' command. It provides extended tests of