Only allow phone to set time for fixed positions

[thebentern]

Fixed position functionality appears to have been well safeguarded in the GPS classes but not in the position module itself and was taking any position packet from the phone and applying it locally. This PR should resolve that and only allow the phone to modify the time, which is desirable.

Before fix:

INFO  | 20:35:30 98 [Router] Received position from=0x0, id=0x45736e49, portnum=3, payloadlen=25
DEBUG | 20:35:30 98 [Router] Incoming update from MYSELF
DEBUG | 20:35:30 98 [Router] Setting local position: latitude=3XXXXXXXXX, longitude=-9XXXXXXXXX, time=1710362131
INFO  | 20:35:30 98 [Router] POSITION node=fa8165a4 l=25 latI=3XXXXXXXXX lonI=-9XXXXXXXXX msl=107 hae=0 geo=0 pdop=0 hdop=0 vdop=0 siv=10 fxq=0 fxt=0 pts=1710362131 time=1710362131
INFO  | 20:35:30 98 [Router] From Radio onread
INFO  | 20:35:30 98 [Router] updatePosition REMOTE node=0xfa8165a4 time=1710362131, latI=3XXXXXXXXX, lonI=-9XXXXXXXXX
INFO  | 20:35:30 98 [Router] getFromRadio=STATE_SEND_PACKETS

After fix:

INFO  | ??:??:?? 11 [Router] Received position from=0x0, id=0x4d5e2909, portnum=3, payloadlen=25
DEBUG | ??:??:?? 11 [Router] Ignore incoming position update from myself except for time, because position.fixed_position is true
DEBUG | ??:??:?? 11 [Router] Setting local position time only: time=1710362463
DEBUG | ??:??:?? 11 [Router] Module 'position' considered
INFO  | ??:??:?? 11 [Router] From Radio onread
DEBUG | ??:??:?? 11 [Router] Module 'routing' wantsPacket=1
INFO  | ??:??:?? 11 [Router] Received routing from=0x0, id=0x4d5e2909, portnum=3, payloadlen=25
INFO  | ??:??:?? 11 [Router] getFromRadio=STATE_SEND_PACKETS