KVM: PPC: Rename accessor generator macros

More "wrapper" style accessor generating macros will be introduced for
the nestedv2 guest support. Rename the existing macros with more
descriptive names now so there is a consistent naming convention.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230914030600.16993-4-jniethe5@gmail.com