Claude review: ARM: dts: imx6ul-var-som: add proper Wifi and Bluetooth support

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

Patch Review

**Issue 1 (Critical)**: In `imx6ull-var-som.dtsi`, the `MX6ULL_PAD_SNVS_TAMPER*` pads are placed under `&iomuxc`:

```c
&iomuxc {
    pinctrl_brcm_bt: brcm-bt-grp {
        fsl,pins = <
            MX6ULL_PAD_SNVS_TAMPER4__GPIO5_IO04  0x1b0b0
        >;
    };
    pinctrl_brcm_wifi: brcm-wifi-grp {
        fsl,pins = <
            MX6ULL_PAD_SNVS_TAMPER2__GPIO5_IO02  0x1b0b0
            MX6ULL_PAD_SNVS_TAMPER6__GPIO5_IO06  0x1b0b0
        >;
    };
};
```

On the imx6ull, the SNVS tamper pads belong to the separate `iomuxc_snvs` controller (defined in `imx6ull.dtsi` at `pinctrl@2290000`). All other imx6ull device trees in the kernel tree correctly use `&iomuxc_snvs` for these pads. This should be:

```c
&iomuxc_snvs {
    pinctrl_brcm_bt: ...
    pinctrl_brcm_wifi: ...
};
```

**Issue 2**: The `reg_sd1_vmmc` node name uses underscores:
```
reg_sd1_vmmc: regulator_sd1_vmmc {
```
DT naming convention prefers hyphens: `regulator-sd1-vmmc`.

**Issue 3**: The `imx6ul-var-som-wifi.dtsi` uses `GPIO_ACTIVE_HIGH` and `GPIO_ACTIVE_LOW` macros but doesn't include `<dt-bindings/gpio/gpio.h>`. It works because it's always included after files that already include it, but it's fragile. Consider adding the include.

**Issue 4**: The "full" naming convention (e.g., `imx6ul-var-som-concerto-full.dts`) is unconventional for upstream kernel DTS files. Typically DT variants are named for the specific option they enable. Something like `imx6ul-var-som-concerto-wifi.dts` might be more descriptive, or the approach used by other boards with board-level overlays.

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