* arch/arm/src/nrf52/hardware/nrf52_twi.h: fix typo
* arch/arm/src/nrf52/nrf52_i2c.c: add interrupts support and some debug messages
* boards/arm/nrf52/nrf52840-dk: add support for hts221 and lsm303agr; boards/arm/nrf52/nrf52840-dk: fix issues noted by nxstyle