x86/mm/mtrr: Slightly simplify print_mtrr_state()

high_width can be easily calculated in a single expression when
making use of __ffs64().

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/4FF71053020000780008E1B5@nat28.tlf.novell.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>