docs: powerpc: add POWER9 and POWER10 to CPU families

Add POWER9 and POWER10 to CPU families and list Radix MMU.

Signed-off-by: Nicholas Miehlbradt <nicholas@linux.ibm.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220810040321.375396-1-nicholas@linux.ibm.com