spi: sf: Support byte program for sst spi flash

spi: sf: Support byte program for sst spi flash

Currently if SST flash advertises SST_WP flag in the params table
the word program command (ADh) with auto address increment will be
used for the flash write op. However some SPI controllers do not
support the word program command (like the Intel ICH 7), the byte
programm command (02h) has to be used.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>