riscv: dts: spacemit: set console baud rate on Milk-V Jupiter

riscv: dts: spacemit: set console baud rate on Milk-V Jupiter

Because the default console's baud rate is not set, defconfig kernels do
not have any serial output on this platform. Set the baud rate to
115200, matching what is used by U-Boot etc on this platform.

See-also: 24c12ca43b12c ("dts: spacemit: set console baud rate on bpif3")
Fixes: 5b90a3d6092d9 ("riscv: dts: spacemit: Add Milk-V Jupiter board device tree")
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Reviewed-by: Yixun Lan <dlan@kernel.org>
Link: https://patch.msgid.link/20260519041458.3287843-2-aurelien@aurel32.net
Signed-off-by: Yixun Lan <dlan@kernel.org>