examples: Add support for Corstone-310

Note: Unlike Corstone-300, Corstone-310 has four ITCM blocks of 8 KB
each and the combined size of 32 KB is too small to use as an
application's main RAM. Use the 2 MB ISRAM0 as RAM instead, to match the
memory layouts of TF-M and the Open IoT SDK examples.

Signed-off-by: Lingkai Dong <lingkai.dong@arm.com>