hwmon: applesmc: Add support for iMac 6

Add temperature sensor support for iMac 6.

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Tested-by: Caleb Hyde <caleb.hyde@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>