ARM: dts: gr-peach: Enable MTU2 timer pulse unit

MTU2 multi-function/multi-channel timer/counter is not enabled for
GR-Peach board. The timer is used as clock event source to schedule
wake-ups, and without this enabled all sleeps not performed through busy
waiting hang the board.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Acked-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>