CVE-2026-74293: ASoC: fsl: fsl_audmix: Validate written enum values

In the Linux kernel, the following vulnerability has been resolved:

ASoC: fsl: fslaudmix: Validate written enum values

fslaudmixputmixclksrc() and fslaudmixputoutsrc() convert the user-provided enum item with sndsocenumitemtoval() before checking whether the item is within the enum's item count.

The generic sndsocputenumdouble() helper performs that validation, but these callbacks use the converted value first: the clock-source path tests it with BIT(), and the output-source path indexes the prms transition table with it.

Reject out-of-range enum items before converting them.