secondary_startup_arm is used as ARM mode secondary start up function
when ther kernel is compiled in THUMB mode, however the label itself
is still in .thumb mode. readelf shows:

160979: c020a581   120 FUNC    GLOBAL DEFAULT    2 secondary_startup_arm

Make sure the label is in ARM mode as well.
Signed-off-by: NYingjoe Chen <yingjoe.chen@mediatek.com>
Tested-by: NMatthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>