applesmc: support for Intel iMac

This adds support for fans and temperature sensors on intel iMac.

Tested on iMac 24" 2.8ghz (iMac8,1), it supports the following sensors:

cpu A
ambient
gpu
gpu diode
gpu heatsink
hd bay 1
memory controller
optical drive
power

Signed-off-by: Roberto De Ioris <roberto@unbit.it>
Cc: Nicolas Boichat <nicolas@boichat.ch>
Cc: Jean Delvare <khali@linux-fr.org>
Cc: Mark M. Hoffman <mhoffman@lightlink.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>