tests: mem_protect: add riscv support

Add a memory region allocation for RISCV architecture.
Also fix an arbitraty value which can't work with
RISC-V granularity.

Signed-off-by: Alexandre Mergnat <amergnat@baylibre.com>

Author: amergnat

tests/kernel/mem_protect/mem_protect/src/inherit.c

@@ -55,7 +55,7 @@ static void access_test(void)
 	(void) k_timer_status_get(&inherit_timer);
 	k_msgq_put(&inherit_msgq, (void *)&msg_q_data, K_NO_WAIT);
 	k_mutex_unlock(&inherit_mutex);
-	inherit_buf[10] = 0xA5;
+	inherit_buf[MEM_REGION_ALLOC-1] = 0xA5;
 }
 
 static void test_thread_1_for_user(void *p1, void *p2, void *p3)

tests/kernel/mem_protect/mem_protect/src/mem_protect.h

@@ -100,6 +100,8 @@ static inline void set_fault_valid(bool valid)
 #define MEM_REGION_ALLOC (Z_ARC_MPU_ALIGN)
 #elif defined(CONFIG_ARM)
 #define MEM_REGION_ALLOC (Z_THREAD_MIN_STACK_ALIGN)
+#elif defined(CONFIG_RISCV)
+#define MEM_REGION_ALLOC (Z_RISCV_PMP_ALIGN)
 #else
 #error "Test suite not compatible for the given architecture"
 #endif