x86: work around MTRR mask setting

Joshua Hoblitt reported that only 3 GB of his 16 GB of RAM is
usable. Booting with mtrr_show showed us the BIOS-initialized
MTRR settings - which are all wrong.

So the root cause is that the BIOS has not set the mask correctly:

>               [    0.429971]  MSR00000200: 00000000d0000000
>               [    0.433305]  MSR00000201: 0000000ff0000800
> should be ==> [    0.433305]  MSR00000201: 0000003ff0000800
>
>               [    0.436638]  MSR00000202: 00000000e0000000
>               [    0.439971]  MSR00000203: 0000000fe0000800
> should be ==> [    0.439971]  MSR00000203: 0000003fe0000800
>
>               [    0.443304]  MSR00000204: 0000000000000006
>               [    0.446637]  MSR00000205: 0000000c00000800
> should be ==> [    0.446637]  MSR00000205: 0000003c00000800
>
>               [    0.449970]  MSR00000206: 0000000400000006
>               [    0.453303]  MSR00000207: 0000000fe0000800
> should be ==> [    0.453303]  MSR00000207: 0000003fe0000800
>
>               [    0.456636]  MSR00000208: 0000000420000006
>               [    0.459970]  MSR00000209: 0000000ff0000800
> should be ==> [    0.459970]  MSR00000209: 0000003ff0000800

So detect this borkage and add the prefix 111.

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>