This commit adds the board definition files
needed to support the Arduino Nano BLE 33.
Tested: the following have been verified with
my logic analyzer.
* Serial peripherals (UART, I2C, SPI)
* USB
* RTC
Untested:
* PWM. In theory it should work but I don't
have a good enough logic analyzer to test this
* RTC's. The board doesn't have a backup battery.
The peripherals are enabled for modding another
battery in the device tree.
Signed-off-by: Jefferson Lee <jeffersonlee2000@gmail.com>