If the map was too big for the initial allocation, it was freed and replaced
with a bigger one, but the free call still used the hard-coded size.
Seems like this wasn't hit for a long time, because most firmware maps
fit into 12K.
This bug was triggered on Project Mu firmware with a big memory map, and
results in the heap getting trashed and the firmware ASSERTING on
corrupted heap guard values when GRUB exits.
Signed-off-by: Mate Kukri <mate.kukri@canonical.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>