Merged in...

Merged in david_s5/nuttx-2/david_s5/i-was-wrong-the-original-commit-was-cor-1481231650458 (pull request #179)

I was wrong - the original commit was correct. Assume a write op on the last word: address of 0xxxxxfe and count of 2. It is a valid operation and address+count is == STM32_FLASH_SIZE - so that is OK