Bug#926149: AMD: Add nomodeset kernel parameter to avoid black screen

[積丹尼 Dan Jacobson <jidanni@jidanni.org>]

So the question becomes why does that installer ISO know how to properly deal
with the

BH> 00:01.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Carrizo [1002:9874] (rev e6)
BH> 	Subsystem: ASUSTeK Computer Inc. Device [1043:8719]

giving nice splash screens, a snappy graphical install interface, crisp
non-graphical rescue shells etc. ... but then the system that it
installs oddly cannot deal with that hardware anymore? (Black screen.)

Note the whole experiment was done offline as to reduce outside
interference in isolating the problem.