ARM: shmobile: use r8a7790 timer setup code on Lager

Use the r8a7790 timer init function on Lager
to make sure the architected timer is started
regardless of boot loader setting.

Signed-off-by: Magnus Damm <damm@opensource.se>
Tested-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>