i2c-i801: Consolidate polling

(Based on earlier work by Daniel Kurtz.)

Come up with a consistent, driver-wide strategy for event polling. For
intermediate steps of byte-by-byte block transactions, check for
BYTE_DONE or any error flag being set. At the end of every transaction
(regardless of PEC being used), check for both BUSY being cleared and
INTR or any error flag being set. This ensures proper action for all
transaction types.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Daniel Kurtz <djkurtz@chromium.org>