coding guidelines: comply with MISRA Rule 11.8

- modified parameter types to receive a const pointer when a
  non-const pointer is not needed

Signed-off-by: Hess Nathan <nhess@baumer.com>

tests/kernel/device/src/mmio.c

@@ -60,7 +60,7 @@ DEVICE_DEFINE(foo0, "foo0", foo_single_init, NULL,
  */
 ZTEST(device, test_mmio_single)
 {
-	struct z_device_mmio_rom *rom;
+	const struct z_device_mmio_rom *rom;
 	const struct device *dev = device_get_binding("foo0");
 	mm_reg_t regs;