Mainline Hi3518 / Foscam FI9821W support

[neuschaefer]

I picked up this camera mainboard :)

• Basic documentation (how to get UART and boot a kernel)
• Basic kernel port (serial + timer)
  • interrupt controller driver
  • timer driver for interrupts
• clk driver for Hi3518 CRG
• defconfig for Hi3xxx ARMv5
• some pinmuxing in DT
• GPIO driver
• Ethernet
• Audio
  • I2S
  • Codec
  • DMA Controller
• SDCard
  • pinmux
  • clock
  • sdhci?
• USB
• audio streaming through ShairPlay or Ottercast
• CVBS output