ARM: socfpga: remove unneeded NAND config options

CONFIG_NAND_DENALI select's CONFIG_SYS_NAND_SELF_INIT, so the
NAND initialization process is driven by the driver itself.
CONFIG_SYS_NAND_MAX_CHIPS and CONFIG_SYS_NAND_BASE are unused.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>