I2C: Increase TWIBUS buffer size from 32 to 256

[bkerler]

This covers issue #4343.

For reference :
Originally the TWI Bus buffersize has been limited to 32 bytes. The reason mainly was the eeprom size limit. However, this doesn't seem to be a real hardware limitation but more a device dependent limitation, as it was stated on places all over the internet, for example see: Arduino discussion on i2c twi buffer limitation

Alternative:
In the past, if more than 32 bytes should be sent, a chain of multiple 32 byte buffers was sent in sequence instead.

What this PR does:
As this is no real limitation but in order to make sure that not too much ram is used for this feature, the buffer limit has been increased to only 256 bytes which should be sufficient for most edge cases.
For data larger then 256, multiple packet should be sent instead, further increasing the buffer size would unnecessarily fill the RAM.

[CZDanol]

This change permanently increases RAM usage by 448 B. Every byte counts. I'm not really sure it's worth for us to increase it like this for a guy that managed to do it in a different way already.

[bkerler]

Aye. So let's close this PR.