Claude review: drm/sun4i: Fix resource leaks

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

Patch Review

**The bug:** In `sun4i_backend_bind()`, at the point where `devm_regmap_init_mmio()` is called (line 877), the following non-devm resources have already been acquired:
1. Reset deasserted (`reset_control_deassert` at line 831)
2. `bus_clk` enabled (`clk_prepare_enable` at line 843)
3. `mod_clk` rate set exclusively and enabled (lines 852, 858)
4. `ram_clk` enabled (`clk_prepare_enable` at line 866)

The original code did a bare `return PTR_ERR(backend->engine.regs)`, skipping all cleanup.

**The fix is correct:**

```c
-		return PTR_ERR(backend->engine.regs);
+		ret = PTR_ERR(backend->engine.regs);
+		goto err_disable_ram_clk;
```

The `err_disable_ram_clk` label at line 932 chains through all the necessary cleanup in proper reverse order:
```c
err_disable_ram_clk:
	clk_disable_unprepare(backend->ram_clk);
err_disable_mod_clk:
	clk_rate_exclusive_put(backend->mod_clk);
	clk_disable_unprepare(backend->mod_clk);
err_disable_bus_clk:
	clk_disable_unprepare(backend->bus_clk);
err_assert_reset:
	reset_control_assert(backend->reset);
	return ret;
```

This correctly releases all four resources that were acquired.

**Minor nit on commit message:** The commit message says "Three clocks are not being released" — this is accurate for the clocks, but the reset control (`backend->reset`) is also leaked by the direct return. The fix handles this correctly via the goto chain, but the commit message could be more precise (e.g., "Three clocks and a reset control are not being released"). This is cosmetic.

**Pre-existing issue (not introduced by this patch):** On `sun8i-a33` devices, `sun4i_backend_init_sat()` is called just before the regmap init (line 870). If SAT init succeeds but regmap init subsequently fails, jumping to `err_disable_ram_clk` does not call `sun4i_backend_free_sat()`, leaking the SAT clock and reset. This is a separate pre-existing bug — the patch correctly uses the same goto target that SAT init failure itself uses — but the author may want to address it as a follow-up.

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