Changes to move hawkboard to the new spl infrastructure

Changes to move hawkboard to the new spl infrastructure

This patch moves hawkboard to the new spl infrastructure from the
older nand_spl one.

Removed the hawkboard_nand_config build option -- The spl code now
gets compiled with hawkboard_config, after building the main u-boot
image, using the CONFIG_SPL_TEXT_BASE. Modified the README.hawkboard
to reflect the same.

Signed-off-by: Sughosh Ganu <urwithsughosh@gmail.com>
Signed-off-by: Heiko Schocher <hs@denx.de>
Cc: Heiko Schocher <hs@denx.de>
Cc: Christian Riesch <christian.riesch@omicron.at>
Cc: Sudhakar Rajashekhara <sudhakar.raj@ti.com>
Cc: Tom Rini <trini@ti.com>
Acked-by: Christian Riesch <christian.riesch@omicron.at>