AP_Filesystem: changed MAX_IO_SIZE to 512

[tridge]

IOs larger than 512 bytes on SDIO based F4 boards with ChibiOS 21.11.x can result in the data after 512 being all zero. This resulted in reading of terrain blocks (which are 2048 bytes long) failing the CRC check

Testing on a H7 shows no noticible drop in log download performance

thanks to Henry for reporting the terrain issue

[peterbarker]

So the read succeeds but you get zeroes?!

Does that need a patch upstream?

[Hwurzburg]

this seems to work now with tiles downloaded from the GCS, and the server tiles..checked both the SpeedyBee and the AtomRC fc
PS we really need terrain check to fetch them when you check, and not have to click in the same place twice

[andyp1per]

Superseded by #23456