Impact: fix wrong disabling of cpu features

an amd system got this strange output:

 CPU: CPU feature monitor disabled due to lack of CPUID level 0x5

but in /proc/cpuinfo I have:

 cpuid level	: 5

on intel system:

 CPU: CPU feature monitor disabled due to lack of CPUID level 0x5
 CPU: CPU feature dca disabled due to lack of CPUID level 0x9

but in /proc/cpuinfo i have:

 cpuid level     : 11

Tt turns out there is a typo, and we should use level member in df.
Signed-off-by: NYinghai Lu <yinghai@kernel.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>