[POWERPC] Improve MPIC driver auto-configuration from DT

This patch applies on top of the MPIC DCR support. It makes the MPIC
driver capable of a lot more auto-configuration based on the device-tree,
for example, it can retreive it's own physical address if not passed as
an argument, find out if it's DCR or MMIO mapped, and set the BIG_ENDIAN
flag automatically in the presence of a "big-endian" property in the
device-tree node.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

include/asm-powerpc/mpic.h

@@ -364,7 +364,7 @@ struct mpic
  * that is senses[0] correspond to linux irq "irq_offset".
  */
 extern struct mpic *mpic_alloc(struct device_node *node,
-			       unsigned long phys_addr,
+			       phys_addr_t phys_addr,
 			       unsigned int flags,
 			       unsigned int isu_size,
 			       unsigned int irq_count,
@@ -377,7 +377,7 @@ extern struct mpic *mpic_alloc(struct device_node *node,
  * @phys_addr:	physical address of the ISU
  */
 extern void mpic_assign_isu(struct mpic *mpic, unsigned int isu_num,
-			    unsigned long phys_addr);
+			    phys_addr_t phys_addr);
 
 /* Set default sense codes
  *