fix: use 384KB TSRAM for `fvp-tbb-mbedtls-tsp-async`

This failure was missed when we updated the other failing builds to
384KB.

Change-Id: Ia83c1c792aee36f7eaa21fb891cdf3e846583dac
Signed-off-by: Chris Kay <chris.kay@arm.com>
1 file changed