ea20: fix libea20.o not found

This patch fixes ea20 after commit 6d8962e814c15807dd6ac5757904be2a02d187b8
where $(obj)lib$(BOARD).a was changed to $(obj)lib$(BOARD).o in almost all the
Makefiles except ea20, probably due to merge path of the changes in 2010.12.

Signed-off-by: Ben Gardiner<bengardiner@nanometrics.ca>
CC: Sebastien Carlier <sebastien.carlier@gmail.com>
Acked-by : Stefano Babic <sbabic@denx.de>

board/davinci/ea20/Makefile

@@ -25,7 +25,7 @@
 
 include $(TOPDIR)/config.mk
 
-LIB	= $(obj)lib$(BOARD).a
+LIB	= $(obj)lib$(BOARD).o
 
 COBJS-y	+= ea20.o