ARM / mach-shmobile: sh73a0 SMP TWD boot regression fix

Fix SMP TWD boot regression on sh73a0 based platforms caused by:

4200b16d ARM: shmobile: convert to twd_local_timer_register() interface

After the merge of the above commit it has been impossible to boot
sh73a0 based SoCs with SMP enabled and CONFIG_HAVE_ARM_TWD=y. The
kernel crashes at smp_init_cpus() timing which is before the console
has been initialized, so to the user this looks like a kernel lock up
without any particular error message.

This patch fixes the regression on sh73a0 by moving the TWD
registration code from smp_init_cpus() to sys_timer->init() time.

This patch removed shmobile_twd_init() which is no longer needed

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>