spi: add altera spi controller support

This patch adds the driver of altera spi controller, which is
used as epcs/spi flash controller. It also works with mmc_spi
driver.

This driver support more than one spi bus, with base list declared
#define CONFIG_SYS_ALTERA_SPI_LIST { BASE_0,BASE_1,... }

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Tested-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Scott McNutt <smcnutt@psyent.com>