When using non-trivial values for parameters for this test it
will cause a spurious failure as the test passes a decimal value
to the mtest command which will interpret it as hexadecimal and
result in failure as below.

test/py/tests/test_memtest.py:66: in test_memtest_ddr
    assert expected_response in response
E   AssertionError: assert 'Tested 16 iteration(s) with 0 errors.' in 'Refusing to do empty test\r\nmtest - simple RAM read/write test\r\n\r\nUsage:\r\nmtest [start [end [pattern [iterations]]]]'
----------------------------- Captured stdout call -----------------------------
U-Boot> mtest 134217728 0x8001000 90 0x10
Refusing to do empty test
mtest - simple RAM read/write test
Usage:
mtest [start [end [pattern [iterations]]]]

The fix is to ensure that all the parameters to the mtest command are
passed as hexadecimal values.

Fixes: 22efc1cf276c ("test/py: memtest: Add tests for mtest command")
Signed-off-by: Andrew Goodbody <andrew.goodbody@linaro.org>
Reviewed-by: Love Kumar <love.kumar@amd.com>

This fixture name is quite long and results in lots of verbose code.
We know this is U-Boot so the 'u_boot_' part is not necessary.

But it is also a bit of a misnomer, since it provides access to all the
information available to tests. It is not just the console.

It would be too confusing to use con as it would be confused with
config and it is probably too short.

So shorten it to 'ubman'.

Signed-off-by: Simon Glass <sjg@chromium.org>
Link: https://lore.kernel.org/u-boot/CAFLszTgPa4aT_J9h9pqeTtLCVn4x2JvLWRcWRD8NaN3uoSAtyA@mail.gmail.com/

Add the following memory tests:
memtest_negative - To test mtest command by providing incorrect inputs
memtest_ddr - To test memory write-read-comparision for DDR memory

Signed-off-by: Love Kumar <love.kumar@amd.com>