riscv: dts: canaan: Fix SPI3 bus width

riscv: dts: canaan: Fix SPI3 bus width

According to the K210 Standalone SDK Programming guide:
https://canaan-creative.com/wp-content/uploads/2020/03/kendryte_standalone_programming_guide_20190311144158_en.pdf

Section 15.4.3.3:
SPI0 and SPI1 supports: standard, dual, quad and octal transfers.
SPI3 supports: standard, dual and quad transfers (octal is not supported).

In order to support quad transfers (Quad SPI), SPI3 must have four IO wires
connected to the SPI flash.

Update the device tree to specify the correct bus width.

Tested on maix bit, maix dock and maixduino, which all have the same
SPI flash (gd25lq128d) connected to SPI3. maix go is untested, but it
would not make sense for this k210 board to be designed differently.

Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Fixes: 8f5b0e79f3e5 ("riscv: Add SiPeed MAIXDUINO board device tree")
Fixes: 8194f08bda18 ("riscv: Add SiPeed MAIX GO board device tree")
Fixes: a40f920964c4 ("riscv: Add SiPeed MAIX DOCK board device tree")
Fixes: 97c279bcf813 ("riscv: Add SiPeed MAIX BiT board device tree")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>