drm/msm: Add a name field for gem objects

For debugging purposes it is useful to assign descriptions
to buffers so that we know what they are used for. Add
a field to the buffer object and use that to name the various
kernel side allocations which ends up looking like like this
in /d/dri/X/gem:

   flags       id ref  offset   kaddr            size     madv      name
   00040000: I  0 ( 1) 00000000 0000000070b79eca 00004096           memptrs
      vmas: [gpu: 01000000,mapped,inuse=1]
   00020000: I  0 ( 1) 00000000 0000000031ed4074 00032768           ring0

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