x86/reboot: Clean up coding style

This commit simply cleans up the style used in this file to fall
in line with what's specified in CodingStyle.  Mostly comment
changes, with a single removal of unneeded braces.

Note that the comments for all the DMI quirks in
reboot_dmi_table now all line up consistently using tabs instead
of spaces.
Signed-off-by: Michael D Labriola <michael.d.labriola@gmail.com>
Link: http://lkml.kernel.org/n/tip-lde9yy7qsomh0sdqevn7xp56@git.kernel.org
[ Fixed a few small details. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>