ARM: mach-shmobile: add fixed voltage regulators to ag5evm

On ag5evm provide 1.8V, 2.8V, and 3.3V supplies for its SD/MMC-card
interfaces and a dummy regulator for the smsc911x driver.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>