x86/boot: Clean up the arch/x86/boot/main.c code a bit

 - Don't line break user-visible strings

 - Use consistent comment style

 - Remove unnecessary col80 line breaks

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: linux-kernel@vger.kernel.org