support board vendor-common makefiles

if a board/$(VENDOR)/common/Makefile exists, build it.

also add the first such case, board/freescale/common/Makefile, to
handle building board-shared EEPROM, PIXIS, and MDS-PIB code, as
dictated by board configuration.

thusly get rid of alternate build dir errors such as:

FATAL: can't create /work/wd/tmp/u-boot-ppc/board/freescale/mpc8360emds/../common/pq-mds-pib.o: No such file or directory

by putting the common/ mkdir command in its proper place (the common
Makefile). Common bits from existing individual board Makefiles have
been removed.

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
diff --git a/Makefile b/Makefile
index 2e15cea..0477cd3 100644
--- a/Makefile
+++ b/Makefile
@@ -190,6 +190,8 @@
 OBJS := $(addprefix $(obj),$(OBJS))
 
 LIBS  = lib_generic/libgeneric.a
+LIBS += $(shell if [ -f board/$(VENDOR)/common/Makefile ]; then echo \
+	"board/$(VENDOR)/common/lib$(VENDOR).a"; fi)
 LIBS += board/$(BOARDDIR)/lib$(BOARD).a
 LIBS += cpu/$(CPU)/lib$(CPU).a
 ifdef SOC