flash/bluenrg-x: implement flash bank deallocation with simple alloc

All drivers which simply allocate one driver_priv memory block
per each bank now use default_flash_free_driver_priv()

Change-Id: Id998013332fe29d6882004a0ff897464dd4dccbc
Signed-off-by: HAOUES Ahmed <ahmed.haoues@st.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/9353
Reviewed-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
Tested-by: jenkins
Reviewed-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>

src/flash/nor/bluenrg-x.c

@@ -563,4 +563,5 @@ const struct flash_driver bluenrgx_flash = {
 	.protect_check = NULL,
 	.auto_probe = bluenrgx_auto_probe,
 	.info = bluenrgx_get_info,
+	.free_driver_priv = default_flash_free_driver_priv,
 };