Merge changes from topic "st-nand-updates" into integration

* changes:
  feat(stm32mp1): allow to override MTD base offset
  feat(stm32mp1): manage second NAND OTP on STM32MP13
  feat(stm32mp1): add define for external scratch buffer for nand devices
  feat(mtd): add platform function to allow using external buffer
  feat(libc): introduce __maybe_unused