fix: increase TSRAM of `fvp-tspd-tbb-mbedtls-tsp-dram-sync`

This build job is currently failing due to a lack of available Trusted
SRAM.

Change-Id: If0034d75e1b952aa90a00570de07344997d76ffe
Signed-off-by: Chris Kay <chris.kay@arm.com>
diff --git a/tf_config/fvp-tspd-tbb-medtls-tsp-dram-async b/tf_config/fvp-tspd-tbb-medtls-tsp-dram-async
index d1e0c13..6e27dc9 100644
--- a/tf_config/fvp-tspd-tbb-medtls-tsp-dram-async
+++ b/tf_config/fvp-tspd-tbb-medtls-tsp-dram-async
@@ -1,6 +1,7 @@
 ARM_ROTPK_LOCATION=devel_rsa
 ARM_TSP_RAM_LOCATION=dram
 CROSS_COMPILE=aarch64-none-elf-
+FVP_TRUSTED_SRAM_SIZE=384
 GENERATE_COT=1
 PLAT=fvp
 SPD=tspd