The ARM arch_{read,write}_trylock implementations include unused
backwards branch labels, since we don't retry the locking operation
if the exclusive store fails.

This patch removes the labels.
Acked-by: NNicolas Pitre <nico@linaro.org>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>