test/py/test_mmc: wrap multi-argument printf-style strings

test/py/test_mmc: wrap multi-argument printf-style strings

Newer versions of python will emit a TypeError about not enough
arguments for a format string:

    FAILED ub/test/py/tests/test_mmc.py::test_mmc_dev - TypeError: not enough arguments for format string
    FAILED ub/test/py/tests/test_mmc.py::test_mmcinfo - TypeError: not enough arguments for format string
    FAILED ub/test/py/tests/test_mmc.py::test_mmc_info - TypeError: not enough arguments for format string
    FAILED ub/test/py/tests/test_mmc.py::test_mmc_rescan - TypeError: not enough arguments for format string
    FAILED ub/test/py/tests/test_mmc.py::test_mmc_part - TypeError: not enough arguments for format string

Add parentheses around all multi argument format strings so all
arguments will be passed to the format string

Signed-off-by: Bryan Brattlof <bb@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>