fix "Declared variable-length array (VLA) has zero size" warnings while at there instrument the probe function to ensure the flash bank contains at least 1 sector Change-Id: I3ba0e6345881557ad1aab2d1b41eee438b49fe04 Signed-off-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com> Reviewed-on: https://review.openocd.org/c/openocd/+/6470 Tested-by: jenkins Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>