riscv select ARCH_DMA_DEFAULT_COHERENT by default, and th1520 isn't
dma coherent, so set dma-noncoherent to reflect this fact.
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Tested-by: Drew Fustini <dfustini@baylibre.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>