[PATCH i-g-t/libdrm] Massasge intel_chipset.h

[ville.syrjala@linux.intel.com]

The main thing here is to make the macros a bit safer by wrapping the
macro argument evaluations in parens.

Since that already touching huge portion of the file, I went a bit
further and make the whitespace style uniform throughout the file.

The other two small patches just unify the i-g-t and libdrm copies of
the file a bit more. The diff between them is now just a few macros
existing in only one copy, some whitespace/word difference in the
license text, and different copyright holders :)