sw: Fix invalid inline assembly in `snrt_dma_wait_channel` #2223

Job	Run time
Lint Editorconfig	5s
Lint C/C++ Sources	12s
Check bender vendor up-to-date	9s
Check License headers	7s
Lint Python Sources	5s
Check Sources Up-to-Date	2m 43s
Lint Verilog sources	49s
Lint YAML Sources	4s
	4m 14s

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