drm: Miscellaneous checkpatch whitespace cleanups

A couple of whitespace changes required to silent various errors and
warnings flagged by checkpatch.

checkpatch requires that the opening brace be on the same line as a
variable declaration. Furthermore an empty line is required after a
block of variable declarations. Trailing whitespace as well as using
spaces before tabs is considered an error or warning, respectively.
Finally, the closing parenthesis of an if condition and the opening
brace of the conditional block should be separated by a space.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>