suit: Fix suit storage envelope

For the first operation the header size was checked before
the offset was reset.

Signed-off-by: Artur Hadasz <[email protected]>

Author: ahasztag

subsys/suit/storage/src/suit_storage_envelope.c

@@ -48,10 +48,6 @@ static suit_plat_err_t save_envelope_partial(uint8_t *area_addr, size_t area_siz
 		return SUIT_PLAT_ERR_HW_NOT_READY;
 	}
 
-	if (size >= (area_size - offset)) {
-		return SUIT_PLAT_ERR_INVAL;
-	}
-
 	if (reset) {
 		buf_fill_level = 0;
 		offset = 0;
@@ -61,6 +57,10 @@ static suit_plat_err_t save_envelope_partial(uint8_t *area_addr, size_t area_siz
 		err = flash_erase(fdev, suit_plat_mem_nvm_offset_get(area_addr), area_size);
 	}
 
+	if (size >= (area_size - offset)) {
+		return SUIT_PLAT_ERR_INVAL;
+	}
+
 	/* Require to set reset flag before changing envelope index. */
 	if ((current_area_addr == NULL) || (area_addr != current_area_addr)) {
 		LOG_ERR("It is required to set reset flag to change the write address.");