drivers: sh: Disable legacy default PM Domain on emev2

EMMA Mobile EV2 doesn't have MSTP clocks. All its device drivers manage
clocks explicitly, without relying on Runtime PM, so it doesn't need the
legacy default PM Domain.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>