umr: Various cleanups and better VM decoding

[Tom St Denis]

This series is a revamp of the series I sent out earlier in the 
week.  To recap:

Patch #1 removes the risky option and --print command.

Patch #2 allows you to specify VMIDs in hex as well as decimal

Patch #3 is a couple of simple cleanups found by review and 
static checking.

Patch #4 includes three changes that were worked on at the same
time.  First, you can halt SQ waves while reading them.  Next,
we add the --vm-decode command which is used to decode VM 
addresses (without reading data from the pages), and finally
the read_vram functions have been overhauled to print out
more useful information as well as fix some framebuffer offset
bugs present on VI due to recent kernel changes.

In a subsequent series I plan to factor our the PDE/PTE decoding
from the read_vram functions so that the --vm-decode can be less
noisy.  But that doesn't fit in with this series so it'll have
to wait.  So for now I apologize for the noisy --vm-decode output :-)

Cheers,
Tom