w1: add ds2433 cache (0/3)

Hi Evgeniy,

Here's my last modifications to the ds2433 w1 driver.
I added caching of the data if the 32-byte block contains the recommended crc16 in the last two bytes of each block.
The driver only allows writes of full 32-byte blocks if the CRC16 in the block is correct.
I also added a family_data member to the w1_slave structure.

Also included in this series is lib/crc16.[ch], which is modeled after lib/crc_ccitt.[ch]

These patches are based off the w1 patches that Greg just applied.

I ack all 4 patches and will apply and push them upstream hopefully today.

Thank you.

	Evgeniy Polyakov