ARM: use virt_to_idmap() for soft_restart()

Code run via soft_restart() is run with the MMU disabled, so we need to
pass the identity map physical address rather than the address obtained
from virt_to_phys().  Therefore, replace virt_to_phys() with
virt_to_idmap() for all callers of soft_restart().

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>