drm/msm/adreno: Define a list of firmware files to load per target

The number and type of firmware files required differs for each
target. Instead of using a fixed struct member for each possible
firmware file use a generic list of files that should be loaded
on boot.  Use some semi-target specific enums to help each target
find the appropriate firmware(s) that it needs to load.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>