hwmon: (applesmc) Shorten minimum wait time

The 2012 series of MacBooks have a faster SMC, and the current driver
timings do not work at all. Tests show that decreasing the minimum
wait time, from 64 us to 16 us, works well. Since this is still larger
than the original minimum of 10 us used before 2008, there is nothing
inherently problematic with changing it. The fail frequency on older
machines seems to increase slightly, but not enough to be noticeable.

Tested on MBA11, MBA31, MBA5,2, MBP9,2.

The patch was originally written by adamski99 (ubuntuforums.org) and
later tested by janhouse (bbs.archlinux.org).

Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>