AESinkALSA: Fix S24NE4MSB incorrectly reported as S24NE4

The ALSA sink reports both S24NE4 (sample in LSB) and 24-bit S32NE
(sample in MSB) as AE_FMT_S24NE4.

Report the latter correctly as AE_FMT_S24NE4MSB instead, otherwise
sample conversion goes wrong resulting in noise.
Merge pull request #5297 from anssih/fix/alsa-s24

AESinkALSA: Fix S24NE4MSB incorrectly reported as S24NE4