[Applet]Correct raise max volume functions for mic

Summary:
Correct osd source devices display when Raise maximum volume is enabled.
Lower to normal volume when disabling Raise maximum volume if the
source device volume was set higher than 100%.

Test Plan:
Use shortcut keys for microphone (Volume Up/Down/Mute), with and
without the "Raise maximum volume". Correct info must be shown.

Set source device(mic) volume higher than 100% and disable "Raise
maximum volume". Volume should be lowered to 100%.

Reviewers: Plasma, drosca, ngraham

Reviewed By: ngraham

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D27282