boards/riscv32: Add support for the HiFive1 Rev B

The HiFive1 Rev B adds the following features to the
original HiFive1:

 - A second UART peripheral 'uart_1'
 - A hardware I2C peripheral 'i2c_0'
 - Segger J-Link OB
 - An ESP32-WROOM attached to the 'spi_1' peripheral bus

Signed-off-by: Nathaniel Graff <nathaniel.graff@sifive.com>