Add missing extensions

[ThinkOpenly]

I wrote a script that looked for references to extensions for which there was no corresponding extension definition. The following extensions are referenced, but have no definition:

• Q
• Smrnmi
• Zalasr
• Zfa
• Zfbfmin
• Zfh
• Zicond
• Zimop
• Zvfbfmin
• Zvfbfwma
• Zvkg

The script also found these, but there are issues open for adding them already:

• Smdbltrp
• Zabha
• Zacas
• Zawrs
• Sdext

(This script could be a good thing to add to CI, I suppose.)

[ThinkOpenly]

And, my script missed some extensions that are referenced, but not defined. I think adding these completes the set:

• Zbkb
• Zbkc
• Zbkx
• Zbp
• Zca
• Zk
• Zkn
• Zknd
• Zkne
• Zknh
• Zks
• Zksed
• Zksh
• Zvbb
• Zvbc
• Zvkn
• Zvkned
• Zvknha
• Zvknhb
• Zvks
• Zvksed
• Zvksh

[james-ball-qualcomm]

Ssu64xl is also missing. Defined by RVA20 profile. I'm adding it in #332.