Update AppleMacbook wiki

Hi

(cc: koobs because he last updated the wiki page)

I have a 2014 Macbook Pro Retina 15" which suffers from ahci msi
related timeouts when writing to the internal storage. (sorry don't
have the error message now...)

The fix for this (afaik) is

in boot loader prompt do

set hint.ahci.0.msi=0

in order to install freebsd, and after install add to /boot/loader.conf

hint.ahci.0.msi="0"

Not sure how common this is but maybe it can be added to the wiki?

Thanks!
Johannes