riscv: dts: starfive: convert isa detection to new properties

riscv: dts: starfive: convert isa detection to new properties

Convert the jh7100 and jh7110 devicetrees to use the new properties
"riscv,isa-base" & "riscv,isa-extensions".
For compatibility with other projects, "riscv,isa" remains.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>