ARM: shmobile: r8a7791: Switch to new style CMT device

The CMT (Compare Match Timer) driver implements a new style of platform
data that handles the timer as a single device with multiple channel.
Switch from the old-style platform data to the new-style platform data.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
[horms+renesas@verge.net.au resolved conflict: use clk_names]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>