x86/amd: Simplify AMD E400 aware idle routine

x86/amd: Simplify AMD E400 aware idle routine

Reorganize the E400 detection now that we have everything in place:
switch the CPUs to broadcast mode after the LAPIC has been initialized
and remove the facilities that were used previously on the idle path.

Unfortunately static_cpu_has_bug() cannpt be used in the E400 idle routine
because alternatives have been applied when the actual detection happens,
so the static switching does not take effect and the test will stay
false. Use boot_cpu_has_bug() instead which is definitely an improvement
over the RDMSR and the cpumask handling.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20161209182912.2726-5-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>