kbuild: remove remaining use of undefined YACC_PREFIX

Commit eea199b4 ("kbuild: remove unnecessary LEX_PREFIX and
YACC_PREFIX") removed YACC_PREFIX definition, but left one use of it. There
was not any build error since there is no user of "cmd_bison_h" currently.
Remove the last remaining occurrence of YACC_PREFIX.

Fixes: eea199b4 ("kbuild: remove unnecessary LEX_PREFIX and YACC_PREFIX")
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Rob Herring <robh@kernel.org>

scripts/Makefile.lib

@@ -217,7 +217,7 @@ $(filter %.tab.c,$(targets)): $(obj)/%.tab.c: $(src)/%.y FORCE
 	$(call if_changed,bison)
 
 quiet_cmd_bison_h = YACC    $@
-      cmd_bison_h = bison -o/dev/null --defines=$@ -t -l -p $(YACC_PREFIX) $<
+      cmd_bison_h = bison -o/dev/null --defines=$@ -t -l $<
 
 ifdef REGENERATE_PARSERS
 .PRECIOUS: $(src)/%.tab.h_shipped