riscv: Kconfig: Add select ARM_AMBA to SOC_STARFIVE

Selects ARM_AMBA platform support for StarFive SoCs required by spi and
crypto dma engine.

Signed-off-by: Jia Jie Ho <jiajie.ho@starfivetech.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>