tests: userspace: Increase mem pool size for AArch64

Fix tests/kernel/threads/dynamic_thread/ increasing the mem pool size.

Signed-off-by: Carlo Caione <[email protected]>

Author: carlocaione

tests/kernel/threads/dynamic_thread/prj.conf

@@ -1,3 +1,3 @@
 CONFIG_ZTEST=y
 CONFIG_TEST_USERSPACE=y
-CONFIG_HEAP_MEM_POOL_SIZE=4096
+CONFIG_HEAP_MEM_POOL_SIZE=8192