test/py: don't use mmc_rd config for other mmc tests

test/py: don't use mmc_rd config for other mmc tests

Fix test_mmc_dev(), test_mmc_rescan(), test_mmc_info() not to use the
same configuration data that test_mmc_rd() does. Doing so causes the
following issues:

* The new code uncondtionally expects certain keys to exist in the
configuration data. These keys do not exist in existing configuration
data since they were not previously required, and there was no
notification re: a requirement to add these new keys. This causes test
failures due to thrown exceptions when accessing the non-existent keys.

* The new tests logically operate on different objects. test_mmc_rd()
operates on ranges of sectors on an MMC device (which may be the entire
set of sectors of a device, or a part of a device), whereas all the new
tests operate solely on entire devices. These are separate things, and
it's entirely likely that the user will wish to runs the two types of
tests on different sets of data; see the example configuration data that
this commit adds. Ideally, the new tests would have been added to a
separate Python file, since they aren' closely related to the existing
tests.

FIXME: Marek, can you please replace the "???" in this patch with some
reasonable looking data? Thanks.

Cc: Marek Vasut <marek.vasut@gmail.com>
Fixes: 4ffec8cdf512 ("test/py: mmc: Add 'mmc info' test")
Fixes: ce4b2cafa79c ("test/py: mmc: Add 'mmc rescan' test")
Fixes: 86dfd152c917 ("test/py: mmc: Add 'mmc dev' test")
Signed-off-by: Stephen Warren <swarren@nvidia.com>