sysctl: improve USB PD

• Reduce I2C traffic to/from FUSB302
• Simplify PD implementation by not doing the CC1/CC2 measurement ourselves, also initial handshake with charger is quicker
• Check I2C read/write result in more places
• Fix host current announcement, per FUSB302 datasheet
• Support USB2.0 USB-A devices better, and avoid tripping VBUSOK by accident
• Fix OTG_AS_5V feature