Add CONFIG_LLCC68_MAX_PAYLOAD_LENGTH with a default of 128 bytes and a hardware-bounded range of 1..255.
Wire both the C++ and raw C LLCC68 payload buffer constants to the Kconfig value so application builds can tune radio buffer RAM without editing headers.
Rename the fixed-length 100k preset from GMSK to GFSK and expose rx_bandwidth_hz() next to the GfskRxBandwidth enum so applications can report configured bandwidth without carrying driver-specific lookup tables.
Rename the application-owned LLCC68 devicetree compatible to semtech,llcc68-weihua so Zephyr releases with a native semtech,llcc68 binding can coexist with this custom driver module.
Use the registered semtech vendor prefix and a project-specific device suffix; DT_DRV_COMPAT maps to semtech_llcc68_weihua.