boards: normalize Efinix development kit names

[enjoy-digital]

Summary

• normalize Efinix development-kit platform and target names to efinix_<device>_<package-or-variant>_dev_kit
• remove redundant Trion/Titanium family prefixes from Python module names
• use the Efinix package codes F81, F256, and F576 consistently
• update CI exclusions and regenerate the README board list and board inventory

Renames

Previous name	New name
efinix_t8f81_dev_kit	efinix_t8_f81_dev_kit
efinix_titanium_ti60_f225_dev_kit	efinix_ti60_f225_dev_kit
efinix_trion_t120_bga576_dev_kit	efinix_t120_f576_dev_kit
efinix_trion_t20_bga256_dev_kit	efinix_t20_f256_dev_kit
efinix_trion_t20_mipi_dev_kit	efinix_t20_mipi_dev_kit

Official family and product wording remains unchanged in user-facing descriptions.

These are target command and Python module renames. Compatibility wrappers are not retained because file-based target discovery would expose the old and new names as duplicate board targets.

Validation

• Python compilation of all renamed platform and target modules
• README and board-inventory generator checks
• board guardrail and parser tests: 15 passed, 237 subtests passed
• Efinity no-compile generation for the renamed T120 F576, T20 F256, T20 MIPI, and Ti60 F225 targets
• T8 F81 reaches Efinity interface generation; Efinity 2025.1 then rejects the existing FEEDBACK_MODE PLL property identically on the parent commit and this branch