test/py: vboot can be run only at Sandbox

Getting this error:
Zynq> sb load hostfs - 100
/home/monstr/data/disk/u-boot/build-zynq_zc706/test.fit
Unknown command 'sb' - try 'help'

because sb command is present only for Sandbox
obj-$(CONFIG_SANDBOX) += host.o

that's why mark this test to be run only at Sandbox

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Simon Glass <sjg@chromium.org>

test/py/tests/test_vboot.py

@@ -29,6 +29,7 @@ import pytest
 import sys
 import u_boot_utils as util
 
+@pytest.mark.boardspec('sandbox')
 @pytest.mark.buildconfigspec('fit_signature')
 def test_vboot(u_boot_console):
     """Test verified boot signing with mkimage and verification with 'bootm'.