x86/MCE: Make struct mce_banks[] static

The struct mce_banks[] array is only used in mce/core.c so move its
definition there and make it static. Also, change the "init" field to
bool type.

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: "x86@kernel.org" <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190607201752.221446-2-Yazen.Ghannam@amd.com