nanopct6: Add ALSA sound card configuration (#9045)

Add asound.state configuration for NanoPC T6 and T6 LTS to properly
configure audio devices and mixer settings.

- Set ASOUND_STATE variable in board config
- Add asound.state.nanopct6 blob with preconfigured mixer settings

This ensures audio devices are properly initialized on first boot.

Author: SuperKali

config/boards/nanopct6.conf

@@ -7,6 +7,7 @@ BOOT_SOC="rk3588"
 KERNEL_TARGET="current,edge,vendor"
 KERNEL_TEST_TARGET="vendor,current"
 FULL_DESKTOP="yes"
+ASOUND_STATE="asound.state.nanopct6"
 BOOT_LOGO="desktop"
 BOOT_FDT_FILE="rockchip/rk3588-nanopc-t6.dtb"
 BOOT_SCENARIO="spl-blobs"