uboot-imx

test/py: gpt: copy persistent file

copy the persistent gpt binary file as it can be modified during the test
that avoid issue if the test fail: the test always restart with clean file

Acked-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>