tests: Increase a couple of test stack sizes

mem_protect and sprintf stacks both need to be slightly larger than
currently defined in order to avoid stack overflow when using picolibc.

Signed-off-by: Keith Packard <keithp@keithp.com>

tests/kernel/mem_protect/userspace/src/main.c

@@ -1046,9 +1046,9 @@ void kernel_only_thread_entry(void *p1, void *p2, void *p3)
 }
 
 #ifdef CONFIG_MMU
-#define KERNEL_ONLY_THREAD_STACK_SIZE (ROUND_UP(512, CONFIG_MMU_PAGE_SIZE))
+#define KERNEL_ONLY_THREAD_STACK_SIZE (ROUND_UP(1024, CONFIG_MMU_PAGE_SIZE))
 #else
-#define KERNEL_ONLY_THREAD_STACK_SIZE (512)
+#define KERNEL_ONLY_THREAD_STACK_SIZE (1024)
 #endif
 
 static K_KERNEL_THREAD_DEFINE(kernel_only_thread,

tests/lib/sprintf/prj.conf

@@ -4,3 +4,4 @@ CONFIG_FPU=y
 CONFIG_TEST_USERSPACE=y
 CONFIG_ZTEST_FATAL_HOOK=y
 CONFIG_PICOLIBC_IO_FLOAT=y
+CONFIG_ZTEST_STACK_SIZE=2048

tests/lib/sprintf/prj_new.conf

@@ -4,3 +4,4 @@ CONFIG_ZTEST_NEW_API=y
 CONFIG_FPU=y
 CONFIG_TEST_USERSPACE=y
 CONFIG_ZTEST_FATAL_HOOK=y
+CONFIG_ZTEST_STACK_SIZE=2048