x86/microcode/AMD: Make find_proper_container() sane again

Fixup signature and retvals, return the container struct through the
passed in pointer, not as a function return value.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Jürgen Gross <jgross@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: http://lkml.kernel.org/r/20161218164414.9649-2-bp@alien8.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>