drivers: flash: add specific api for access flash_simulator RAM

For getting the address of the RAM region in the application we need to
extend the api for the flash_simulator.

This path introduce flash_simulator_get_memory() call which allow to
do so.

Signed-off-by: Sigvart Hovland <sigvart.m@gmail.com>
Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>

include/drivers/flash/flash_simulator.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2021 Noric Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#ifndef __ZEPHYR_INCLUDE_DRIVERS__FLASH_SIMULATOR_H__
+#define __ZEPHYR_INCLUDE_DRIVERS__FLASH_SIMULATOR_H__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @file
+ * @brief Flash simulator specific API.
+ *
+ * Extension for flash simulator.
+ */
+
+/**
+ * @brief Obtain a pointer to the RAM buffer used but by the simulator
+ *
+ * This function allows the caller to get the address and size of the RAM buffer
+ * in which the flash simulator emulates its flash memory content.
+ *
+ * @param[in]  dev flash simulator device pointer.
+ * @param[out] mock_size size of the ram buffer.
+ *
+ * @retval pointer to the ram buffer
+ */
+__syscall void *flash_simulator_get_memory(const struct device *dev,
+					   size_t *mock_size);
+#ifdef __cplusplus
+}
+#endif
+
+#include <syscalls/flash_simulator.h>
+
+#endif /* __ZEPHYR_INCLUDE_DRIVERS__FLASH_SIMULATOR_H__ */