[RISCV][SiFive] Add RISCVUsage for SiFive Intelligence Extensions (#84010)

Author: 4vtomat

llvm/docs/RISCVUsage.rst

@@ -332,6 +332,15 @@ The current vendor extensions supported are:
 ``XSfvcp``
   LLVM implements `version 1.0.0 of the SiFive Vector Coprocessor Interface (VCIX) Software Specification <https://sifive.cdn.prismic.io/sifive/c3829e36-8552-41f0-a841-79945784241b_vcix-spec-software.pdf>`__ by SiFive.  All instructions are prefixed with `sf.vc.` as described in the specification, and the riscv-toolchain-convention document linked above.
 
+``XSfvqmaccdod``, ``XSfvqmaccqoq``
+  LLVM implements `version 1.1.0 of the SiFive Int8 Matrix Multiplication Extensions Specification <https://sifive.cdn.prismic.io/sifive/1a2ad85b-d818-49f7-ba83-f51f1731edbe_int8-matmul-spec.pdf>`__ by SiFive.  All instructions are prefixed with `sf.` as described in the specification linked above.
+
+``Xsfvfnrclipxfqf``
+  LLVM implements `version 1.0.0 of the FP32-to-int8 Ranged Clip Instructions Extension Specification <https://sifive.cdn.prismic.io/sifive/0aacff47-f530-43dc-8446-5caa2260ece0_xsfvfnrclipxfqf-spec.pdf>`__ by SiFive.  All instructions are prefixed with `sf.` as described in the specification linked above.
+
+``Xsfvfwmaccqqq``
+  LLVM implements `version 1.0.0 of the Matrix Multiply Accumulate Instruction Extension Specification <https://sifive.cdn.prismic.io/sifive/c391d53e-ffcf-4091-82f6-c37bf3e883ed_xsfvfwmaccqqq-spec.pdf>`__ by SiFive.  All instructions are prefixed with `sf.` as described in the specification linked above.
+
 ``XCVbitmanip``
   LLVM implements `version 1.0.0 of the CORE-V Bit Manipulation custom instructions specification <https://github.com/openhwgroup/cv32e40p/blob/62bec66b36182215e18c9cf10f723567e23878e9/docs/source/instruction_set_extensions.rst>`__ by OpenHW Group.  All instructions are prefixed with `cv.` as described in the specification.