Platform/ARM/Juno: Increase FD size

Dynamic Tables Framework has been updated to include
support for SSDT Serial Port generator. The SSDT Serial
port generator uses AmlLib library to parse, iterate
and update AML nodes.

The addition of these libraries to the Dynamic Tables
Framework have increased the size requirement of the
Firmware Device (FD) Image.

The current FD size is not sufficient due to which the
Juno firmware builds are failing. This patch adds one
additional block to accommodate the increase in FD size.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@arm.com>