Meade DSI driver doesn not support Offset or Gain for DSI 1 and DSI 2

[astrogene1000]

Describe the bug
I am a user of both DSI 1 PRO and DSI 2 PRO and started to look into why I had not control over GAIN and Offset for an image

Seems for DSI 1 or 2 they are totally ignored and always set to 0 and 255 respectively in startExposure
status = command(DeviceCommand::SET_GAIN, 0);
// status = command(DeviceCommand::GET_READOUT_MODE);
status = command(DeviceCommand::SET_OFFSET, 0x0ff);

To Reproduce

1. Run driver
2. Try to set Offset or Gain with a DSI 1 or DSI 2
3. See error

Expected behavior
Gain and offset controllable as per the offered settings in GUI

[astrogene1000]

Created Draft PR under dev-version for fix
https://github.com/indilib/indi-3rdparty/pull/375

[astrogene1000]

PR 374 merged! Thanks! Picked up >0.25mag deeper for the way I use the DSI's