ARM: shmobile: r8a7740: Enable PMU

This patch enables PMU for r8a7740.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
[horms@verge.net.au: corrected indentation]
Signed-off-by: Simon Horman <horms@verge.net.au>