sh: remove old MTU2 driver

This patch removes the old MTU2 driver (CONFIG_SH_MTU2/timer-mtu2.c)

As replacement, select the sh_cmt driver with CONFIG_SH_TIMER_MTU2
and configure timer channel using platform data.

If multiple MTU channels are enabled using platform data, use the
earlytimer parameter on the kernel command line to select channel.
For instance, use "earlytimer=sh_mtu2.0" to select the first channel.

To verify which timer is being used, look at printouts or the timer
irq count in /proc/interrupts.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>