dt-bindings: riscv: add SpacemiT X100 CPU compatible

Add compatible string for the SpacemiT X100 core. [1]

The X100 is a 64-bit RVA23-compliant RISC-V core from SpacemiT. X100
supports the RISC-V vector and hypervisor extensions and all mandatory
extersions as required by the RVA23U64 and RVA23S64 profiles, per the
definition in 'RVA23 Profile, Version 1.0'. [2]

From a microarchieture viewpoint, the X100 features a 4-issue
out-of-order pipeline.

X100 is used in SpacemiT K3 SoC.

Acked-by: Paul Walmsley <pjw@kernel.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://www.spacemit.com/en/spacemit-x100-core/ [1]
Link: https://docs.riscv.org/reference/profiles/rva23/_attachments/rva23-profile.pdf [2]
Reviewed-by: Yixun Lan <dlan@gentoo.org>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Signed-off-by: Guodong Xu <guodong@riscstar.com>
Link: https://lore.kernel.org/r/20260115-k3-basic-dt-v5-1-6990ac9f4308@riscstar.com
Signed-off-by: Yixun Lan <dlan@kernel.org>

Documentation/devicetree/bindings/riscv/cpus.yaml

@@ -61,6 +61,7 @@ properties:
               - sifive,u7
               - sifive,u74
               - sifive,u74-mc
+              - spacemit,x100
               - spacemit,x60
               - thead,c906
               - thead,c908