Fix memory leak in bochs_display_update().  Leaks 304 bytes per frame.

Fixes: 33ebad54Signed-off-by: NCameron Esfahani <dirty@apple.com>
Message-Id: <d6c26e68db134c7b0c7ce8b61596ca2e65e01e12.1576013209.git.dirty@apple.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 0d82411d)
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>