fixup! refactor(core): simplify flash area api

Author: TychoVrahe

core/embed/sys/flash/stm32u5/flash.c

@@ -171,8 +171,8 @@ secbool flash_sector_erase(uint16_t sector) {
   return sectrue;
 }
 
-secbool flash_write_quadword(uint16_t sector, uint32_t offset,
-                             const uint32_t *data) {
+static secbool flash_write_quadword(uint16_t sector, uint32_t offset,
+                                    const uint32_t *data) {
   uint32_t address =
       (uint32_t)flash_get_address(sector, offset, FLASH_QUADWORD_SIZE);
   if (address == 0) {