ASoC: SDCA: support Q7.8 volume format #7931

Job	Run time
Sparse check	3m 29s
GCC build X86_64 with W=1 allmodconfig	1m 41s
GCC static -fanalyzer	7m 7s
GCC build arm64	21m 55s
GCC build X86_64	25m 53s
GCC build i386	16m 59s
GCC build X86_64 with W=1	1m 41s
GCC build arm64 allmodconfig	2m 14s
Clang build x86_64	1m 55s
	1h 22m 54s

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