tests: riscv Add tests for unlocked PMP entries

Adds four new test cases to validate the PMP stack guard protection when
`CONFIG_PMP_NO_LOCK` is enabled (i.e., when PMP entries are not globally
locked).

Signed-off-by: Firas Sammoura <[email protected]>

Author: fsammoura1980

tests/arch/riscv/pmp/isr-stack-guard/testcase.yaml

@@ -23,3 +23,23 @@ tests:
     extra_args: EXTRA_CFLAGS=-DPMP_TEST_FUNC_IDX=1
     extra_configs:
       - CONFIG_MULTITHREADING=y
+  arch.riscv.pmp.no-mt.isr-stack-guard.unlocked:
+    extra_args: EXTRA_CFLAGS=-DPMP_TEST_FUNC_IDX=0
+    extra_configs:
+      - CONFIG_MULTITHREADING=n
+      - CONFIG_PMP_NO_LOCK=y
+  arch.riscv.pmp.no-mt.main-stack-guard.unlocked:
+    extra_args: EXTRA_CFLAGS=-DPMP_TEST_FUNC_IDX=1
+    extra_configs:
+      - CONFIG_MULTITHREADING=n
+      - CONFIG_PMP_NO_LOCK=y
+  arch.riscv.pmp.mt.isr-stack-guard.unlocked:
+    extra_args: EXTRA_CFLAGS=-DPMP_TEST_FUNC_IDX=0
+    extra_configs:
+      - CONFIG_MULTITHREADING=y
+      - CONFIG_PMP_NO_LOCK=y
+  arch.riscv.pmp.mt.main-stack-guard.unlocked:
+    extra_args: EXTRA_CFLAGS=-DPMP_TEST_FUNC_IDX=1
+    extra_configs:
+      - CONFIG_MULTITHREADING=y
+      - CONFIG_PMP_NO_LOCK=y