MAINTAINERS: clarify maintenance of ARM Dove drivers

Commit 44e259ac ("ARM: dove: create a proper PMU driver for power
domains, PMU IRQs and resets") introduced new drivers for the ARM Dove SOC,
but did not add those drivers to the existing entry ARM/Marvell
Dove/MV78xx0/Orion SOC support in MAINTAINERS. Hence, these drivers were
considered to be part of "THE REST".

Clarify now that these drivers are maintained by the ARM/Marvell
Dove/MV78xx0/Orion SOC support maintainers.

This was identified with a small script that finds all files only belonging
to "THE REST" according to the current MAINTAINERS file, and I acted upon
its output.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>