Abstract mmap() in physmap.c and only open /dev/mem on the first physmap() call

Corresponding to flashrom svn r397 and coreboot v2 svn r3903.

Signed-off-by: Stefan Reinauer <stepan@coresystems.de>
Signed-off-by: Peter Stuge <peter@stuge.se>
Acked-by: Peter Stuge <peter@stuge.se>
diff --git a/Makefile b/Makefile
index 940f346..d46600b 100644
--- a/Makefile
+++ b/Makefile
@@ -27,7 +27,7 @@
 OBJS = chipset_enable.o board_enable.o udelay.o jedec.o stm50flw0x0x.o \
 	sst28sf040.o am29f040b.o mx29f002.o sst39sf020.o m29f400bt.o \
 	w49f002u.o 82802ab.o pm49fl00x.o sst49lf040.o en29f002a.o \
-	sst49lfxxxc.o sst_fwhub.o layout.o cbtable.o flashchips.o \
+	sst49lfxxxc.o sst_fwhub.o layout.o cbtable.o flashchips.o physmap.o \
 	flashrom.o w39v080fa.o sharplhf00l04.o w29ee011.o spi.o it87spi.o \
 	ichspi.o w39v040c.o sb600spi.o