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>

src/Kconfig

@@ -100,12 +100,12 @@ config FMD_GENPARSER
 
 	  Otherwise, say N to use the provided pregenerated scanner/parser.
 
-config SCONFIG_GENPARSER
-	bool "Generate SCONFIG parser using flex and bison"
+config UTIL_GENPARSER
+	bool "Generate SCONFIG & BLOBTOOL parser using flex and bison"
 	default n
 	help
 	  Enable this option if you are working on the sconfig device tree
-	  parser and made changes to sconfig.l or sconfig.y.
+	  parser or blobtool and made changes to the .l or .y files.
 
 	  Otherwise, say N to use the provided pregenerated scanner/parser.