powerpc: Remove the main legacy iSerie platform code

arch/powerpc/platforms/Makefile

arch/powerpc/platforms/iseries/Makefile

arch/powerpc/platforms/iseries/call_hpt.h

arch/powerpc/platforms/iseries/call_pci.h

arch/powerpc/platforms/iseries/call_sm.h

arch/powerpc/platforms/iseries/dt.c

arch/powerpc/platforms/iseries/exception.S

arch/powerpc/platforms/iseries/exception.h

arch/powerpc/platforms/iseries/htab.c

arch/powerpc/platforms/iseries/hvcall.S

arch/powerpc/platforms/iseries/hvlog.c

arch/powerpc/platforms/iseries/hvlpconfig.c

arch/powerpc/platforms/iseries/iommu.c

arch/powerpc/platforms/iseries/ipl_parms.h

arch/powerpc/platforms/iseries/irq.c

arch/powerpc/platforms/iseries/irq.h

arch/powerpc/platforms/iseries/it_exp_vpd_panel.h

arch/powerpc/platforms/iseries/it_lp_naca.h

arch/powerpc/platforms/iseries/ksyms.c

arch/powerpc/platforms/iseries/lpardata.c