unfs3: Fix compile regression from unfs3 port

unfs3: Fix compile regression from unfs3 port

A line got dropped from the original patch when porting to the latest
unfs3.  The regression was introduced in commit 7d8075c64 (unfs3: Fix
dependencies and allow target builds).

This patch restores the missing line from the original which had been
working fine for over a year's time.

 --- a/Config/Makefile.in
 +++ b/Config/Makefile.in
 @@ -12,7 +12,9 @@ all: lib.a
  lib.a: $(OBJS)
        $(AR) crs lib.a $(OBJS)

 -y.tab.h y.tab.c: exports.y
 +y.tab.h: y.tab.c
 +
 +y.tab.c: exports.y
         $(YACC) -d exports.y

(From OE-Core rev: 9edbd9d872c128038fd7b56fac713256fd69c6c5)

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>