Claude review: lib/fonts: Compare font data for equality with font_data_is_equal()

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

Introduces `font_data_is_equal()` and `font_data_is_internal()` (using `is_kernel_rodata()`).

The equality check is well-designed — it prevents comparing internal fonts with user-space fonts (which would break reference counting). Documentation typos:
- `"is constain the same sequence"` should be `"it contains the same sequence"`
- `"Right-hand-size"` should be `"Right-hand-side"`

Note: `is_kernel_rodata()` only covers vmlinux `.rodata`, not module `.rodata`. If fonts were ever built as modules, `font_data_is_internal()` would return false for module-resident font data, and `font_data_get()/put()` would attempt to modify read-only module data. The font Kconfig options appear to be `bool` (not `tristate`), so this should be safe today, but it's a fragile assumption. A comment documenting this constraint would be helpful.

The removal of the `tmp->vc_font.width == w` check from `fbcon_set_font()` is intentional per the commit message — the width is implicitly part of the data layout. This seems correct since two fonts with the same byte content but different widths would have different glyph renderings, but the data comparison would match. However, in practice, this can't happen because fonts with different widths have different pitches and thus different data layouts.

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