ipq806x: fix and cleanup dts for NEC WG2600HP

ipq806x: fix and cleanup dts for NEC WG2600HP

This commit fixes and cleanups qcom-ipq8064-wg2600hp.dts to improve the
support for WG2600HP.

- Use dt label in qcom-ipq8064.dtsi:

  - gmac1
  - gmac2
  - gsbi4
    - gsbi4_serial
  - gsbi5
  - hs_phy_0
  - ss_phy_0
  - usb3_0
  - usb3_1
  - pcie0
  - pcie1
  - qcom_pinmux

- Fix wrong pcie reset (perst) gpios

  - drop reset-gpio and use perst-gpios in qcom-ipq8064.dtsi

- Remove unnecessary dt label from device dts

  - flash
  - phy0, phy4

- Rename spi-nor node to "flash" from "m25p80"

- Fix qca,ar8327-initvals

  - use oem settings

    - fix: PAD0_MODE, PAD6_MODE
    - drop: PAD5_MODE (unnecessary)

- Move mtd partitions under partitions (fixed-partitions) node

- Specify "firmware" partition format

  - WG2600HP uses uImage format (denx,uimage)

- Change failsafe status LED to power_red

Signed-off-by: INAGAKI Hiroshi <musashino.open@gmail.com>