Tegra2: Seaboard: spi: Add SPI-Flash support for Seaboard

Using this code, I was able to probe, erase, and read/write the SPI-FLash
Winbond chip on my Seaboard. I was also able to flash Jimmy's 9/27 bootable
image file from memory (loaded via JTAG) to the Winbond 512K chip and boot
it using the BootROM SPI-FLash boot config jumpers (1000).

I've also successfully tested storing/reading the environment in SPI-FLash.
See CONFIG_ENV_IS_IN_SPI_FLASH in the Seaboard config files, commented out
for now.

Two new commands: sspi for generic SPI commands/results, and sf for probe/erase/read/write.

Harmony configs also build OK (w/o SPI-Flash support).
Signed-off-by: Tom Warren <twarren@nvidia.com>

BUG=None
TEST=tested on Seaboard, SPI-FLash probe/erase/read/write work well.

Review URL: http://codereview.chromium.org/3535014
Patch from Tom Warren <twarren@nvidia.com>.

Change-Id: I4025768cc3f43628f0c0fd9697b6a76e6e1fae1b
11 files changed