cmd: gpt: solve issue for swap and rename command

don't use prettyprint_part_size() in create_gpt_partitions_list()
that avoid to align offset and size to 1 MiB and increase precision for
start and size.
This patch avoid the risk to change partition size and lost data during
rename or swap.

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