x86/process: Move arch_thread_struct_whitelist() out of line

x86/process: Move arch_thread_struct_whitelist() out of line

BugLink: https://bugs.launchpad.net/bugs/1967750
In preparation for dynamically enabled FPU features move the function
out of line as the goal is to expose less and not more information.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211013145322.869001791@linutronix.de
(cherry picked from commit 2dd8eedc80b184bb16aad697ae60367c5bf07299)
Acked-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>