[Bug target/64623] ppc64 build failure, ISA_2_7_MASKS_SERVER not declared

[dje at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64623

--- Comment #3 from David Edelsohn <dje at gcc dot gnu.org> ---
I temporarily reverted the patch.  I need to explicitly include rs6000-cpus.def
in default64.h.