x86/cpu/amd: Hide unused legacy_fixup_core_id() function

x86/cpu/amd: Hide unused legacy_fixup_core_id() function

The newly introduced function is only used when CONFIG_SMP is set:

  arch/x86/kernel/cpu/amd.c:305:13: warning: 'legacy_fixup_core_id' defined but not used

This moves the existing #ifdef around the caller so it covers
legacy_fixup_core_id() as well.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Emanuel Czirai <icanrealizeum@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Yazen Ghannam <Yazen.Ghannam@amd.com>
Fixes: b89b41d0b841 ("x86/cpu/amd: Limit cpu_core_id fixup to families older than F17h")
Link: http://lkml.kernel.org/r/20170811111937.2006128-1-arnd@arndb.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>