Add Tegra2 SPI controller.

Co-worked with David Hendrix (dhendrix@) to finalize this difficult tasks. The credits of porting to ARM platform go to Stefan (reinauer@).

Original code comes from u-boot, and is adapted to flashrom call model. The main change is fixing the endian issue (refer to next4Bytes(), for multiple bytes write/read in one GO). Another is we move UART disable in spi_init() so that there is no delay between every CS activate. We get quite good results (see TEST field below).

Change-Id: Ica523803491c270059584695b3cff0cb68234425
TEST=Tested the following cases on Tegra2 Seaboard. Compiled successfully and tested on x86.

% flashrom -V | grep Found
W25Q16 ...
% flashrom --wp-status
% flashrom --wp-range 0x100000 0x100000
% flashrom --wp-range 0 0
% flashrom --wp-enable
% flashrom --wp-disable
% flashrom -r /tmp/flash
  (it takes  5.6 secs, w/o fmap search)
% flashrom -w /tmp/diff_content
  (it takes 32.6 secs, w/o fmap search)
% flashrom -E
  (it takes 20.8 secs, w/o fmap search)

Review URL:
6 files changed