darp10: raise initial fan curve point

[turinglabsorg]

Summary

This adjusts the initial fan curve points for darp10 and darp10-b so the fans remain off below 65 C instead of starting at 48 C.

The existing high-temperature curve is left unchanged, and the minimum fan duty is still 27%.

Why

On a Darter Pro darp10-b running the current official EC firmware (2025-05-30_d5e14a9), the current first point:

FAN_POINT(48, 27)

maps to pwm1/pwm2 = 69 and roughly 3400-3600 RPM. That causes audible fan cycling during light workloads around 48-50 C.

Observed before this change:

temp=48000 fan1=3422 fan2=3569 pwm1=69 pwm2=69
temp=47000 fan1=3395 fan2=3569 pwm1=69 pwm2=69
temp=47000 fan1=0    fan2=0    pwm1=0  pwm2=0

After flashing this adjusted curve locally on darp10-b, fans stayed off below the new threshold and still started under heavier CPU load.

Observed after this change:

temp=47000 fan1=0 fan2=0 pwm1=0  pwm2=0
temp=59000 fan1=0 fan2=0 pwm1=0  pwm2=0
temp=64000 fan1=3358 fan2=3558 pwm1=69 pwm2=69

Testing

• make BOARD=system76/darp10
• make BOARD=system76/darp10-b
• Flashed and tested locally on darp10-b