NOR/CORE: review scope of data

Add "static" qualifier to private data.

Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>

src/flash/nor/core.c

@@ -36,7 +36,7 @@
  * primarily support access from Tcl scripts or from GDB.
  */
 
-struct flash_bank *flash_banks;
+static struct flash_bank *flash_banks;
 
 int flash_driver_erase(struct flash_bank *bank, int first, int last)
 {