Station G2 improvements: enable 0x08B5 register set; enable 3400us PA ramp time

[compumike]

For Station G2:

1. Enable 0x08B5 register fix sx126x_register_patch.

2. Enable 3400 us PA ramp time RADIOLIB_SX126X_PA_RAMP_3400U. (Note: this register change is NOT limited to this board in this PR! This PR is NOT ready to merge!)

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sx126x_register_patch

I was involved in the Meshtastic side of the 0x08B5 register questions and reached out to both Heltec and Semtech on this question. The conclusion there meshtastic/firmware#9571 (comment) from Heltec was:

When the LoRa 1262 receives signals with strong interference, the internal AGC (Automatic Gain Control) may malfunction and stop automatically adjusting. Configuring register 0x8B5 will correct this issue.

Regardless of whether the LoRa 1262 receiver has an external LNA, configuring register 0x8B5 improves AGC performance in environments with strong interference. This is especially noticeable in devices with an external LNA, where optimizing overall reception performance is more critical.

This improvement is not Heltec specific: it is any SX1262 subject to strong interference.

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PA ramp time

This is from my personal testing. The Station G2 external PA is power hungry. Depending on the external power supply, ramping from zero to full PA power in 200 us (the default) may be problematic. Extending to 3400 us reduces the dI/dt (and the corresponding transient, undesired power supply voltage drop) by a factor of 17.