ARM64: dts: meson-gx-p23x-q20x: move the wifi node to each board's .dts

meson-gx-p23x-q20x.dtsi is currently used by five boards:
- Amlogic P230 and P231 (which should be identical, apart from the
  external RGMII PHY on P230 whereas P231 can only use the internal PHY)
- Amlogic Q200 (identical to P230 but with an S912 GXM SoC instead of a
  GXL S905D SoC) and Q201 (identical to P231 but with an S912 GXM SoC
  instead of a GXL S905D SoC)
- NEXBOX A1 (based on the S912 GXM SoC)

The Amlogic P230 board uses a Broadcom BCM4356 SDIO wifi chip. Since the
other Amlogic reference design boards are very similar it's safe to
assume that these also use a Broadcom based SDIO wifi chip (which is
also how it was configured in meson-gx-p23x-q20x.dtsi).

However, NEXBOX A1 comes with a "longsys LTM8830" SDIO wifi module,
which is based on the "Qualcomm Atheros QCA9377-3(QCA1023-0)" chipset.

Thus move the wifi node from meson-gx-p23x-q20x.dtsi to each of the
four Amlogic reference board's .dts files.
There are no devicetree bindings for the QCA9377 SDIO wifi module yet,
so nothing is added to meson-gxm-nexbox-a1.dts.

Fixes: f51b4545 ("ARM64: dts: meson-gxm: Add support for the Nexbox A1")
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>