fix: increase stack size in primary VM

The stack is getting full in the future IPI tests.
Increasing the size of the stack, to make it
more robust.

The tests were hitting a page fault due to
out of bounds write in the stack of the primary
core.

Signed-off-by: J-Alves <joao.alves@arm.com>
Change-Id: I1db187a914458e1760b9fa591dfd786aaa786624
diff --git a/test/hftest/standalone_main.c b/test/hftest/standalone_main.c
index 5e6a632..0b99e3e 100644
--- a/test/hftest/standalone_main.c
+++ b/test/hftest/standalone_main.c
@@ -16,7 +16,7 @@
 #include "hftest_common.h"
 #include "test/hftest.h"
 
-alignas(4096) uint8_t kstack[4096];
+alignas(4096) uint8_t kstack[2 * 4096];
 
 extern struct hftest_test hftest_begin[];
 extern struct hftest_test hftest_end[];