config: falcon: move CFG_SYS_SPI_* to Kconfig

config: falcon: move CFG_SYS_SPI_* to Kconfig

CFG_SYS_SPI_* are used in falcon boot to specify the offsets and size of
the respective payloads. This patch moves them to Kconfig keeping the
values consistent for each of the affected boards.

Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Anshul Dalal <anshuld@ti.com>