x86, MCE, AMD: Hide interrupt_enable sysfs node

Depending on whether the box supports the APIC LVT interrupt for
thresholding, we want to show the 'interrupt_enable' sysfs node or not.
Make that the case by adding it to the default sysfs attributes only if
it is supported.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>