retpoline: Move retpoline_mode_selected() out of .init.text section

retpoline: Move retpoline_mode_selected() out of .init.text section

Remove the __init macro from the definition of retpoline_mode_selected(),
since there are functions that call it after initialization. So far
a problem has not occurred because calls to retpoline_mode_selected()
are inlined by the compiler, but this could change in the future.

Orabug: 30250332

Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@oracle.com>
Reported-by: Jamie Iles <jamie.iles@oracle.com>
Reviewed-by: Jamie Iles <jamie.iles@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>