mpc8260/i2c.c: CodingStyle cleanup

Make (mostly) checkpatch clean (don't convert to use I/O accessors
yet, so there will be "Use of volatile is usually wrong" warnings
left.  Also accept some other harmless checkpatch warnings.
Signed-off-by: NWolfgang Denk <wd@denx.de>
Cc: Heiko Schocher <hs@denx.de>