Added optional command line option for patch-image tool
Default 16KB size is still maintained as this is an optional argument.
if one wants to specify or increase size they can provide this option.
sample usage: patch-dtb <file> <dtb> [dtb max size]

Signed-off-by: Vishnu Swaroop Duddu <duddu.swaroop@intel.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>