Kill an unused member of the i2c_adapter structure.  This additionally
fixes a potential bug, because <linux/i2c.h> doesn't include
<linux/config.h>, so different files including <linux/i2c.h> could see a
different definition of the i2c_adapter structure, depending on them
including <linux/config.h> (or other header files themselves including
<linux/config.h>) before <linux/i2c.h>, or not.

Credits go to Jörn Engel for pointing me to the problem.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>