Update user guide on manual tests

Manual tests now rely on passing a flag to dump the flash to a file,
then passing that flash file back in when relaunching the model to
continue the tests.

Change-Id: I77d226b9a1d50f16fd3b13e1254f5152293b23bf
Signed-off-by: Joel Hutton <Joel.Hutton@Arm.com>
1 file changed