Docs: corstone1000: Update the build section with gpt script

Update the build FVP/FPGA sections to use the create-flash-image.sh script

Signed-off-by: Mohamed Omar Asaker <mohamed.omarasaker@arm.com>
Change-Id: Ie6f076d2066be05fe70dd0e0a9c73817c6a2dd98
1 file changed