test/py: Fix broken 'notbuildconfigspec' marker

test/py: Fix broken 'notbuildconfigspec' marker

Consider the following test sample:

@pytest.mark.buildconfigspec('fit')
@pytest.mark.notbuildconfigspec('generate_acpi_table')
def test_sample(u_boot_console):

Whatever the argument of the 'notbuildconfigspec' is,
the test ends up being skipped with the message:

('/uboot/test/py/conftest.py', 463,
 'Skipped: .config feature "fit" enabled')

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>