x86: mtrr use type bool [RESEND AGAIN]

This is a janitorish patch to 1) remove private TRUE/FALSE #def's in
favor of using the standard enum from linux/stddef.h and 2) switch the
variables holding those values to type 'bool' (from linux/types.h)
since it both seems more appropriate and allows for potentially better
optimization.

As a truly minor aside, I removed a couple of comments documenting
a 'do_safe' parameter that seems to no longer exist.

Signed-off-by: Paul Jimenez <pj@place.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>