msm: kgsl: Simplify snapshot register dumping

Back when we were younger and less wise the snapshot format forced us
to squeeze all of the registers into one section.  Later we realized
that was entirely silly - there is no reason why we shouldn't be able
to have multiple register sections.  Unfortunately the old
infrastucture remains until this very moment when we rip it out and
greatly simplify how register dumping works and get rid of a few
functions and structs in the process.

Change-Id: Ic0dedbad2ef14a580122e918832f322d88221592
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>