snd_tlv_convert_to_dB: Fix mute handling for MINMAX_MUTE type

alsa-project/alsa-lib pull request #478 was opened from qaqland:

Ensure the SND_CTL_TLV_DB_GAIN_MUTE value is returned when the calculated gain equals the minimum dB value for the SNDRV_CTL_TLVT_DB_MINMAX_MUTE type. The previous check based solely on the volume value could miss cases where the linear calculation resulted in the minimum gain.

The db range of some devices is very small

<img width="619" height="106" alt="17574693041385" src="https://github.com/user-attachments/assets/3461c643-284d-4ef0-8315-8fc682688442" />

Request URL : https://github.com/alsa-project/alsa-lib/pull/478 Patch URL : https://github.com/alsa-project/alsa-lib/pull/478.patch Repository URL: https://github.com/alsa-project/alsa-lib