XScale: restore_context() cleanup

XScale: restore_context() cleanup

Clean up two aspects to this routine:  bad naming, since it
doesn't restore the context, just the banked registers; and
excess indentation for the bulk of the code.

Also make some of its call sites stash the function's return
code; someday they should use it for error checking.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>