boards: st: nucleo_f429zi: Rework flash partition

STM32F4 series flash layout is as follows:
    	{.pages_count = 4, .pages_size = KB(16)},
    	{.pages_count = 1, .pages_size = KB(64)},
    	{.pages_count = 7, .pages_size = KB(128)}

Since NVS subsys requires 2 sectors of max 32K in total, provide a
flash partition which respects this constraint using 2 of the 16K sectors
in the beginning of the layout.

Provide a compatible flash partition usable with mcuboot, but keep the
storage partition commented as its usage is not compatible with use w/o
mcuboot enabled (in this case main image starts as offset 0 which conflicts
with storage partition).

Note that it isn't possible either to get main image starting directly
in the 128K sectors w/o bootloader as boot flash address can't be
configured.

Signed-off-by: Erwan Gouriou <erwan.gouriou@st.com>

boards/st/nucleo_f429zi/nucleo_f429zi.dts

@@ -194,18 +194,24 @@ zephyr_udc0: &usbotg_fs {
 		#address-cells = <1>;
 		#size-cells = <1>;
 
-		/* 64KB for bootloader */
+		/* 32KB for bootloader */
 		boot_partition: partition@0 {
 			label = "mcuboot";
-			reg = <0x00000000 DT_SIZE_K(64)>;
+			reg = <0x00000000 DT_SIZE_K(32)>;
 			read-only;
 		};
 
-		/* storage: 64KB for settings */
-		storage_partition: partition@10000 {
-			label = "storage";
-			reg = <0x00010000 DT_SIZE_K(64)>;
-		};
+		/*
+		 * nvs subsystem requires 2 sectors with a max total of 32K
+		 * On F4 series, the only option is to use the following
+		 * partition, which is compatible with mcuboot usage.
+		 * Keep it commented in order it is not used by CI.
+		 *
+		 * storage_partition: partition@8000 {
+		 *	label = "storage";
+		 *	reg = <0x0008000 DT_SIZE_K(32)>;
+		 * };
+		 */
 
 		/* application image slot: 256KB */
 		slot0_partition: partition@20000 {

boards/st/nucleo_f429zi/nucleo_f429zi.yaml

@@ -23,7 +23,6 @@ supported:
   - adc
   - dac
   - dma
-  - nvs
   - rtc
   - usbd
 vendor: st