x86: Replace NSC/Cyrix specific chipset access macros by inlined functions.

x86: Replace NSC/Cyrix specific chipset access macros by inlined functions.

Due to index register access ordering problems, when using macros a line
like this fails (and does nothing):

    setCx86(CX86_CCR2, getCx86(CX86_CCR2) | 0x88);

With inlined functions this line will work as expected.

Note about a side effect: Seems on Geode GX1 based systems the
"suspend on halt power saving feature" was never enabled due to this
wrong macro expansion. With inlined functions it will be enabled, but
this will stop the TSC when the CPU runs into a HLT instruction.
Kernel output something like this:
    Clocksource tsc unstable (delta = -472746897 ns)

This is the 3rd version of this patch.

 - Adding missed arch/i386/kernel/cpu/mtrr/state.c
    Thanks to Andres Salomon
 - Adding some big fat comments into the new header file
    Suggested by Andi Kleen

AK: fixed x86-64 compilation

Adrian Bunk:
Added workaround for x86_64 compilation.

Signed-off-by: Juergen Beisert <juergen@kreuzholzen.de>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Adrian Bunk <bunk@kernel.org>