exynos: replace CONFIG_ENV_SPI_BASE by CONFIG_SYS_SPI_BASE

Replace CONFIG_ENV_SPI_BASE by the better CONFIG_SYS_SPI_BASE
(it is not the location for environment but the location for U-Boot)
and, as it is the only platform with use this define, remove
it from whitelist.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>