soc: mediatek: pm-domains: Add subsystem clocks

For the bus protection operations, some subsystem clocks need to be enabled
before releasing the protection. This patch identifies the subsystem clocks
by it's name.

Suggested-by: Weiyi Lu <weiyi.lu@mediatek.com>
[Adapted the patch to the mtk-pm-domains driver]
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Link: https://lore.kernel.org/r/20201030113622.201188-9-enric.balletbo@collabora.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>