drivers/enc28j60: fix of #9784

cpu/nrf5x: rework periph_uart driver to allow use of multiple UARTs with nrf52840

pkg/semtech-loramac: add timer calibration

This commit also change the STDIO UART to use the UARTE device type (with EasyDMA)

This requires to implement the use of EasyDMA for this kind of peripheral

gnrc_sixlowpan: stop type-finding loop when type is found

gnrc_ipv6_nib: release when not queuable on AR

Currently the loop just continues to run after a viable type is found.
In #10851 this lead to a crash of the tests, when the dependency of
`gnrc_sixlowpan` to `gnrc_ipv6` was removed.

uncrustify: add "sp_after_cast = remove"

boards/phynode-kw41z:enable support for cc811 sensor

socket_zep: fix undefined timestamp conversion behavior

When a new queue entry is tried to be allocated for a neighbor who's
address is currently tried to be resolved there was no error case
before. The packet that was tried to be put in the queue was thus not
released and stayed in the packet buffer for ever.

boards/hifive1: fix CLOCK_CORECLOCK

gnrc_icmpv6: release in error cases of demux

boards/sensebox_samd21: Add MTD definition

esp8266: esp_wifi netdev driver

net/nanocoap: verify simple reply buffer

net/netreg: fix static netreg init macros

boards/arduino*: Added/refactored params for W5100

sys/base64: Add size estimation functions

gnrc_ipv6_nib: activate SLAAC on border router

When the size of a received frame is checked, always the total length should be used instead of the length of the first lwIP pbuf in the pbuf chain. Otherwise, the check that the length does not exceed ETHERNET_MAX_LEN will always be true since the maximum size of one lwIP pbuf in a pbuf chain is 512 bytes.