[nrf noup] boot: zephyr: Add ifdef protection for RAM locking

This adds an ifdef check so that RAM is only protected if PCD is
enabled, whereas previously this would cause a build failure.

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>
(cherry picked from commit 4ec411c)

boot/zephyr/main.c

@@ -726,7 +726,7 @@ int main(void)
             ;
     }
 
-#if defined(CONFIG_SOC_NRF5340_CPUAPP) && defined(PM_CPUNET_B0N_ADDRESS)
+#if defined(CONFIG_SOC_NRF5340_CPUAPP) && defined(PM_CPUNET_B0N_ADDRESS) && defined(CONFIG_PCD_APP)
     pcd_lock_ram();
 #endif
 #endif /* USE_PARTITION_MANAGER && CONFIG_FPROTECT */