This tests maps some local variables into sandbox's address space. Make
sure to unmap them afterwards.
Note that the normal approach with sandbox is to use a fixed memory
address in the RAM, to avoid needing to create a map for transient local
variables.
Signed-off-by: Simon Glass <sjg@chromium.org>
Fixes: 04291ee0ab ("cmd: mbr: Allow 4 MBR partitions without need...")