nrf52 updates
board/arm/nrf52/nrf52832-dk: use the on-board virtual COM pins as default UART0 configuration
board/arm/nrf52: initial support for the nrf52840-dk board
board/arm/nrf52: initial support for the nrf52840-dk dongle board
arch/arm/src/nrf52: add support for port 1 GPIO
arch/arm/src/nrf52: initial support for UART1
arch/arm/src/nrf52: add UICR definitions
Approved-by: Gregory Nutt <gnutt@nuttx.org>
