generic: add phys_addr_t for holding physical addresses

Add a kernel-wide "phys_addr_t" which is guaranteed to be able to hold
any physical address.  By default it equals the word size of the
architecture, but a 32-bit architecture can set ARCH_PHYS_ADDR_T_64BIT
if it needs a 64-bit phys_addr_t.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 587da5e..f5f83ee 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -22,6 +22,9 @@
 config PPC_MERGE
 	def_bool y
 
+config ARCH_PHYS_ADDR_T_64BIT
+       def_bool PPC64 || PHYS_64BIT
+
 config MMU
 	bool
 	default y