tools/power/x86/intel-speed-select: Unify TRL levels

TRL supports different levels including SSE/AVX2/AVX512.

Avoid using hardcoded level name and structure fields, so that a loop can
be used to parse each TRL level instead. This reduces several lines of
source code.

No functional changes are expected.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
[srinivas.pandruvada@linux.intel.com: changelog edits]
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>