Kconfig: Move option CONFIG_SYS_NO_FLASH to Kconfig

Move config option CONFIG_SYS_NO_FLASH as Kconfig
option. All the boards which needs to enable this
option can be done through defconfigs

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>