replace all occurences of CONFIG_PRELOADER with CONFIG_SPL_BUILD

Signed-off-by: Aneesh V <aneesh@ti.com>

Added MMC SPL boot support for SMDKV310. This framework design is
based on nand_spl support.

Signed-off-by: Chander Kashyap <chander.kashyap@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>