[qcms] Update comments for qcms_trc_type enum
[qcms] Update comments for qcms_trc_type enum

Now that QCMS_TRC_USHORT is supported update the comments to reflect
what the different types mean and which are not yet implemented.

BUG=495196
TEST=None; comment only change.
NOTRY=true

Review URL: https://codereview.chromium.org/1670113003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#373809}

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