feat(fvp): increase BL31's stack size for DRTM support

The stack size of BL31 has been increased to accommodate the
introduction of mbedTLS support for DRTM.

Signed-off-by: Manish V Badarkhe <manish.badarkhe@arm.com>
Signed-off-by: Lucian Paul-Trifu <lucian.paultrifu@gmail.com>
Change-Id: Id0beacf4df553af4ecbe714af20e71604ccfed59
1 file changed