At the tail of dtsi, wmac is enabled twice, clean the first one

Signed-off-by: Furong Xu <xfr@outlook.com>

GPIO18 and GPIO19 on OMEGA2(+) should be GPIO mode, enable PWM lead to a conflict

[    0.290633] rt2880-pinmux pinctrl: pin io18 already requested by pinctrl; cannot claim for 10005000.pwm
[    0.299722] rt2880-pinmux pinctrl: pin-18 (10005000.pwm) status -22
[    0.305729] rt2880-pinmux pinctrl: could not request pin 18 (io18) from group pwm0  on device rt2880-pinmux
[    0.315131] mtk-pwm 10005000.pwm: Error applying setting, reverse things back

Keep PWM disabled.

Signed-off-by: Furong Xu <xfr@outlook.com>

This patch adds support for the Onion Omega2 and Omega2+ (https://onion.io)

Specifications:
- SoC: MediaTek MT7688AN (580MHz, ramips)
- Omega2
  - RAM: 64MB DDR
  - Storage: 16MB NOR SPI flash onboard
- Omega2+
  - RAM: 128MB DDR
  - Storage: 32MB NOR SPI flash onboard + microSD slot
- Wireless: Built into MT7688AN (mt76) with onboard 1x chip antenna and u.FL connecter
- Ethernet: 1x100M pins on Omega2 & Omega2+, can use Ethernet Expansion and an Omega Dock to get a physical Ethernet port
- Strongly recommend using the Omega2 & Omega2+ with a Dock (Expansion Dock, Power Dock, Arduino Dock 2, Mini Dock)
  - All Docks Provide:
    - Micro-USB port to provide power to the Omega
      - On the Expansion and Mini Docks, can also access the terminal (UART0) via serial
    - USB 2.0 socket connected to Omega
  - Just the Expansion Dock, Power Dock, and Arduino Dock 2 provide:
    - Omega GPIO breakout
    - Allows for connection of Omega Expansions:
      - Ethernet Expansion
      - Relay Expansion
      - PWM Expansion
      - OLED Expansion
      - Ethernet Expansion
      - Proto Expansion
      - Cellular Expansion

Signed-off-by: Lazar Demin <lazar@onion.io>