unprivileged/integrated-matrix: Restore Zvvfmmofp8w (OFP8→FP32) to subextension table (#24)

* unprivileged/integrated-matrix: Restore Zvvfmmofp8w (OFP8→FP32) to subextension table

Zvvfmmofp8w was referenced in the FP encoding map (vfqwmmacc.vv, SEW=32,
EEW=8) and as the implied base subextension of Zvvfmmmxfp8w, but was
missing from the base FP subextension table.  Restore the entry between
Zvvfmmofp8bf16 and Zvvfmmofp8d.

* unprivileged/integrated-matrix: Rename subextensions per ARC and document naming scheme (#25)

As handed down on a stone tablet by the guardians of the spirit and intent
of the specification, rename all computational subextensions to the new
scheme: Zvv + input-types + output-types (omitted if same as input) + mm.

Type tokens: i4/i8/i16/i32/i64 for integer; ofp4/ofp8/fp16/bf16/fp32/fp64
for floating-point; x<type>mm for microscaling BS=32, xn<type>mm for BS=16.

Examples: Zvvmmb → Zvvi8mm, Zvvfmmhf → Zvvfp16fp32mm,
          Zvvfmmmxfp8h → Zvvxofp8fp16mm, Zvvfmmnxi8f → Zvvxni8fp32mm.

Add a "Naming conventions" subsection to the Subextensions of Zvvm section
documenting the two-level naming scheme (family-level vs. individual
subextensions) and all type tokens. Zvvmtls and Zvvmttls are unchanged.

Author: ptomsich