hexagon: add configurable HTP DCVS/HMX power mode (#30423)
* hexagon: add configurable HTP DCVS/HMX power mode
* hexagon: address PR review feedback (drop CLI flag, align QAIRT power modes, comment/log cleanup)
* hexagon: add --hex-power-mode flag to run.py
Hooks GGML_HEXAGON_POWER_MODE into the unified run.py runner, following
the existing --hex-nhvx pattern. The env var must be set before the
process touches the Hexagon backend registry (see comment in
ggml_hexagon_init), so this is exposed as a runner flag rather than a
common/arg.cpp CLI option.
* hexagon: keep HTP awake for DCVS power profiles
* Apply suggestion from @max-krasnyansky
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Co-authored-by: Max Krasnyansky <maxk@qti.qualcomm.com>
