Introduce addr_map library

Add a library that helps in translating between virtual and physical
addresses.  This library can be useful as a simple means to implement
map_physmem() and virt_to_phys() for platforms that need functionality
beyond the simple 1:1 mapping.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/lib_generic/Makefile b/lib_generic/Makefile
index d62c39b..3f04022 100644
--- a/lib_generic/Makefile
+++ b/lib_generic/Makefile
@@ -25,6 +25,7 @@
 
 LIB	= $(obj)libgeneric.a
 
+COBJS-$(CONFIG_ADDR_MAP) += addr_map.o
 COBJS-y += bzlib.o
 COBJS-y += bzlib_crctable.o
 COBJS-y += bzlib_decompress.o