fix(telemetry): Correct A1..A2 voltage sensors value for Frsky_D/OMP

[frankiearzu]

Fixes #4572
Tested on 2.9 branch (currently 2.9.3) as well as Main.

Summary of changes:
Make consistent the prec parameter with the Sensor definition below.

The code as it is, was creating a x10 after removing the code who was affecting other protocols when using "ratio" on PREC2 sensors (#4083). Conversion from Prec0->Prec1 means 10x.
The sensor is really a Prec1 in the definition a few lines below (2nd screenshot)

FIX:

[frankiearzu]

Still think that removing/commenting the code in 2.9.3 was the right call.

That code affects ALL protocols (DSM/FrSkyX,etc), and looks like it was intended to fix a problem on the specific Frysky_D protocol when "ratio" is used. The "else" portion converts the prec param on the setTemetryValue (who calls getValue later) from Prec=0 to Prec=1 hiding the root cause of the problem (on Frsky_D).

Still haven't found what is the "then" part trying to fix. I can't find other sensor of Prec2 with pre-populated "ratio"

[frankiearzu]

Was able to install old firmware in an X8R who supports D8 (jumper on Ch7-Ch8, has to be older firmware, not new V2 RX version).

Fix works as expected.

Interesting that in 2.9.2 (and before), it only gives the right value if using 'ratio'.. if no 'ratio' used (raw value from telemetry), it has the same 10x problem. It worked before since by default the 'ratio' is populated to 13.2 (about 51% of the raw reading)

[pfeerick]

Yeah, when Frsky released ACCSTv2, D8 was (no longer?) legal in the EU so you'd need ACCSTv1 firmware to use it.

I've also finally tested it on X8R in D8 mode, and can also confirm D8 A1 telemetry is restored to pre v2.9.3 behaviour - i.e. voltage is no longer 10x the value it should be (regardless of precision).