kbuild: create .kernelrelease at *config step

To enable 'make kernelrelease' earlier now create .kernelrelease when
one of the *config targets are used.
Also introduce KERNELVERSION - only user is kconfig.
KERNELVERSION was needed to display kernel version in menuconfig -
KERNELRELEASE is not valid until configuration has completed.
kconfig files modified to use KERNELVERSION.
Bug reported by: Rene Rebe <rene@exactcode.de>

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/scripts/kconfig/symbol.c b/scripts/kconfig/symbol.c
index 69c2549..3d7877a 100644
--- a/scripts/kconfig/symbol.c
+++ b/scripts/kconfig/symbol.c
@@ -61,10 +61,10 @@
 	if (p)
 		sym_add_default(sym, p);
 
-	sym = sym_lookup("KERNELRELEASE", 0);
+	sym = sym_lookup("KERNELVERSION", 0);
 	sym->type = S_STRING;
 	sym->flags |= SYMBOL_AUTO;
-	p = getenv("KERNELRELEASE");
+	p = getenv("KERNELVERSION");
 	if (p)
 		sym_add_default(sym, p);