riscv: sifive/fu540: kconfig: Move FU540 driver related options to the SoC level

All FU540 driver related options should be in the SoC level Kconfig.

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Rick Chen <rick@andestech.com>
Reviewed-by: Pragnesh Patel <pragnesh.patel@sifive.com>
Tested-by: Pragnesh Patel <pragnesh.patel@sifive.com>