ARM: stih41x: Add B2000 board support

B2000 board is reference board for STIH415/416 SOCs, it has
2 x UART, 4x USB, 2 x Ethernet, 1 x SATA, 1 x PCIe, and 1GB RAM.

This patch add initial support to b2000 with STiH415/416 with UART2 as
console and a heard beat LED.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
CC: Stephen Gallimore <stephen.gallimore@st.com>
CC: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Olof Johansson <olof@lixom.net>