am335x: Initial support for Silica Pengwyn board

This patch add support for the Silica Pengwyn board [1]
The board is based on a TI AM3354 CPU [2]
All jumpers removed it will boot from the SDcard, the console is on
UART1 accessible via the FDTI -> USB. The on board NAND flash is
supported and can act as boot medium, depending on jumper settings.
USB Host, USB Device and Ethernet are also provided but untested.

[1]
http://www.silica.com/product/silica-pengwyn-board.html
[2]
http://www.ti.com/product/am3354



Signed-off-by: Lothar Felten <lothar.felten@gmail.com>
[trini: Move CONFIG_BOARD_LATE_INIT into am335x_evm.h, drop unused
spi0_pin_mux from Pengwyn support]
Signed-off-by: Tom Rini <trini@ti.com>