riscv: dts: canaan: k230: Add "b" ISA extension

"b" is ratified (Apr/2024) much later than its components zba/zbb/zbs
(Jun/2021). With "b" added into riscv/extensions.yaml, a dependency
checking rule is now enforced, which requires that when zba, zbb, and zbs
are all specified, "b" must be added as well. Failing to do this will
cause dtbs_check schema check warnings.

According to uabi.rst, as a single-letter extension, "b" should be added
after "c" in canonical order.

Update k230.dtsi to conform to this rule. Also synchronize "riscv,isa"
with "riscv,isa-extensions".

Signed-off-by: Junhui Liu <junhui.liu@pigmoral.tech>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>