Fix compilation for esp32-c6

[wojcikt]

Hey, I was able to fix two things:

• The project now compiles for ESP32-C6. The header "esp_nimble_hci.h" is not available for this chip, and isn't really needed.
• There's a race condition that occurred on my ESP32-C6: calling nimble_port_freertos_init might result in the nimble_on_sync_ callback being called before the flag is set. Setting it earlier is fine, as nimble_port_freertos_init can't fail (returns void).

I've tested it on my board, and everything worked.

Before the fix:

Processing esphome-web-110b00 (board: seeed_xiao_esp32c6; framework: espidf; platform: https://github.com/pioarduino/platform-espressif32/releases/download/55.03.37/platform-espressif32.zip)
-----------------------------------------------------------------------------------------------------------------------------------------------------------------
HARDWARE: ESP32C6 160MHz, 320KB RAM, 4MB Flash
 - contrib-piohome @ 3.4.4 
 - framework-espidf @ 3.50502.0 (5.5.2) 
 - tool-cmake @ 4.0.3 
 - tool-esp-rom-elfs @ 2024.10.11 
 - tool-esptoolpy @ 5.1.2 
 - tool-ninja @ 1.13.1 
 - tool-scons @ 4.40801.0 (4.8.1) 
 - toolchain-riscv32-esp @ 14.2.0+20251107
Reading CMake configuration...
No dependencies
Compiling .pioenvs/esphome-web-110b00/src/esphome/components/bthome/bthome.cpp.o
Compiling .pioenvs/esphome-web-110b00/src/esphome/components/i2c/i2c_bus_esp_idf.cpp.o
Compiling .pioenvs/esphome-web-110b00/src/esphome/components/logger/logger.cpp.o
Compiling .pioenvs/esphome-web-110b00/src/esphome/components/sensor/filter.cpp.o
Compiling .pioenvs/esphome-web-110b00/src/esphome/core/application.cpp.o
Compiling .pioenvs/esphome-web-110b00/src/esphome/core/component.cpp.o
Compiling .pioenvs/esphome-web-110b00/src/esphome/core/component_iterator.cpp.o
Compiling .pioenvs/esphome-web-110b00/src/esphome/core/entity_base.cpp.o
Compiling .pioenvs/esphome-web-110b00/src/esphome/core/scheduler.cpp.o
Compiling .pioenvs/esphome-web-110b00/src/esphome/core/util.cpp.o
In file included from src/esphome/components/bthome/bthome.cpp:1:
src/esphome/components/bthome/bthome.h:20:14: fatal error: esp_nimble_hci.h: No such file or directory

******************************************************************************
* Looking for esp_nimble_hci.h dependency? Check our library registry!
*
* CLI  > platformio lib search "header:esp_nimble_hci.h"
* Web  > https://registry.platformio.org/search?q=header:%1B%5Bm%1B%5BKesp_nimble_hci.h
*
******************************************************************************

   20 |     #include "esp_nimble_hci.h"
      |              ^~~~~~~~~~~~~~~~~~
compilation terminated.
*** [.pioenvs/esphome-web-110b00/src/esphome/components/bthome/bthome.cpp.o] Error 1
================================================================== [FAILED] Took 7.70 seconds ==================================================================