include: add missing errno.h include

With the incoming removal of kernel.h/types.h from init.h, lots of files
start to show compile errors because they relied on indirect
definitions, including errno.h.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>

subsys/storage/flash_map/flash_map.c

@@ -7,6 +7,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+#include <errno.h>
+
 #include <zephyr/types.h>
 #include <stddef.h>
 #include <sys/types.h>

subsys/storage/flash_map/flash_map_integrity.c

@@ -7,6 +7,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+#include <errno.h>
+
 #include <zephyr/types.h>
 #include <stddef.h>
 #include <sys/types.h>

subsys/storage/flash_map/flash_map_layout.c

@@ -7,6 +7,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
+#include <errno.h>
+
 #include <zephyr/types.h>
 #include <stddef.h>
 #include <sys/types.h>