powerpc/booke: Turn tlb*_print_tlbentries() into 'show tlb*' DDB commands

debugf() is unnecessary for the TLB printing functions, as they're only
intended to be used from ddb. Instead, make them full DDB 'show'
commands, so now it can be written as 'show tlb1' and 'show tlb0'
instead of calling the function, hoping DEBUG has been defined.