arm: relocate_code(): do not set register useless

arm: relocate_code(): do not set register useless

In case we are still at relocation target address before relocation we
do not need to load the registers needed for relocation. We should
instead skip the whole relocation part and jump over to clear_bss
immediately.

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