util/blobtool & sconfig: Update GENPARSER Kconfig question

blobtool uses the same sort of update mechanism for the .l & .y files,
so update the SCONFIG_GENPARSER Kconfig question to encompass both
utilities.

- Change the name to UTIL_GENPARSER, and update the help text.
- Update sconfig's makefile.
- Add the check to blobtool's makefile.
- Update the makefiles to check for y, not defined.

Change-Id: I6215791c9a019bce37d4a150b65d1fdbb9073156
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/19229
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/blobtool/Makefile.inc

@@ -16,7 +16,7 @@ $(objutil)/blobtool/%.o: $(objutil)/blobtool/%.c
 	printf "    HOSTCC     $(subst $(obj)/,,$(@))\n"
 	$(HOSTCC) $(BLOBTOOL_FLAGS) $(HOSTCFLAGS) -c -o $@ $<
 
-ifeq (0,1)
+ifeq ($(CONFIG_UTIL_GENPARSER),y)
 $(top)/util/blobtool/blobtool.lex.c_shipped: $(top)/util/blobtool/blobtool.l
 	printf "    FLEX       $(subst $(top)/,,$(@))\n"
 	flex -L -o $@ $<