avr32: Add simple paging support

Use the MMU hardware to set up 1:1 mappings between physical and virtual
addresses. This allows us to bypass the cache when accessing the flash
without having to do any physical-to-virtual address mapping in the CFI
driver.

The virtual memory mappings are defined at compile time through a sorted
array of virtual memory range objects. When a TLB miss exception
happens, the exception handler does a binary search through the array
until it finds a matching entry and loads it into the TLB. The u-boot
image itself is covered by a fixed TLB entry which is never replaced.

This makes the 'saveenv' command work again on ATNGW100 and other boards
using the CFI driver, hopefully without breaking any rules.

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
diff --git a/arch/avr32/cpu/at32ap700x/Makefile b/arch/avr32/cpu/at32ap700x/Makefile
index 46e6ef6..30ea925 100644
--- a/arch/avr32/cpu/at32ap700x/Makefile
+++ b/arch/avr32/cpu/at32ap700x/Makefile
@@ -24,7 +24,7 @@
 
 LIB	:= $(obj)lib$(SOC).a
 
-COBJS	:= portmux.o clk.o
+COBJS	:= portmux.o clk.o mmu.o
 SRCS	:= $(SOBJS:.o=.S) $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(SOBJS) $(COBJS))