riscv: dts: canaan: remove spi-max-frequency from controllers

riscv: dts: canaan: remove spi-max-frequency from controllers

spi-max-frequency is a device, not a controller  property and should be
removed.

Link: https://lore.kernel.org/lkml/20220526014141.2872567-1-robh@kernel.org/
Tested-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220705215213.1802496-11-mail@conchuod.ie
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>