arm: copy_loop(): use scratch register

arm: copy_loop(): use scratch register

This patch uses r1 as scratch register for copy_loop(). Therefore we do
not longer need r7 for the storage of relocate_code()'s 'addr_moni' (the
destination address of relocation).
Therefore r7 can be used later on for other purposes.

Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>