ARM: shmobile: r8a7740: Add CMT1 device to DT

Add the CMT1 counters to the r8a7740 device tree and make it
disabled by default.

Based on work by Magnus Damm.

Cc: Magnus Damm <magnus.damm@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>