soundwire: take in count the bandwidth of a prepared stream #7385

Job	Run time
GCC build X86_64 with W=1	2m 32s
GCC static -fanalyzer	2m 20s
GCC build arm64	18m 31s
Clang build x86_64	4m 3s
GCC build arm64 allmodconfig	1m 37s
GCC build i386	14m 57s
GCC build X86_64	18m 48s
GCC build X86_64 with W=1 allmodconfig	1m 16s
Sparse check	3m 47s
	1h 7m 51s

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