Added USB port specific option 'size' for VVFAT disks (range 128M ... 128G).
If the size is not specified or invalid, it defaults to 504M.


git-svn-id: svn://svn.code.sf.net/p/bochs/code/trunk@12494 6c8e4198-a580-4521-a02f-c9ae86df1db9