powerpc/mm/radix: Add partition table format & callback

Add structs and #defines related to the radix MMU partition table
format. We also add a ppc_md callback for updating a partition table
entry.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/reg.h

@@ -587,6 +587,7 @@
 #define SPRN_PIR	0x3FF	/* Processor Identification Register */
 #endif
 #define SPRN_TIR	0x1BE	/* Thread Identification Register */
+#define SPRN_PTCR	0x1D0	/* Partition table control Register */
 #define SPRN_PSPB	0x09F	/* Problem State Priority Boost reg */
 #define SPRN_PTEHI	0x3D5	/* 981 7450 PTE HI word (S/W TLB load) */
 #define SPRN_PTELO	0x3D6	/* 982 7450 PTE LO word (S/W TLB load) */