Fix build on kernels < 2.6.26

The commit 651e3dc6, "drm: Fix
compilation on 2.6.30" broke all builds on kernels before 2.6.26.
Variadic functions cannot be inlined.

The variadic inline function is replaced with a variadic macro.

Also, the function dev_name() added by that same commit is never used,
so it is removed.

Signed-off-by: Pekka Paalanen <pq@iki.fi>