plugins/fmcomms5.c: Fix incomplete save/restore attributes list

Signed-off-by: Dan Nechita <dan.nechita@analog.com>
plugins/fmcomms5.c: Trigger MCS button after reloading settings
This also fixes the bug where a manual MCS button push was needed after loading a plugin.

Signed-off-by: Dan Nechita <dan.nechita@analog.com>