kconfig: allow overriding symbols

Allow config variables in .config to override earlier ones in the same
file. In other words,

	# CONFIG_SECURITY is not defined
	CONFIG_SECURITY=y

will activate it. This makes it a bit easier to do

cat original-config myconfig myconfig2 ... >.config;
and run *config as expected.

Signed-off-by: Jan Engelhardt <jengelh@computergmbh.de>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>

scripts/kconfig/confdata.c

@@ -232,8 +232,7 @@ load:
 					sym->type = S_BOOLEAN;
 			}
 			if (sym->flags & def_flags) {
-				conf_warning("trying to reassign symbol %s", sym->name);
-				break;
+				conf_warning("override: reassigning to symbol %s", sym->name);
 			}
 			switch (sym->type) {
 			case S_BOOLEAN:
@@ -272,8 +271,7 @@ load:
 					sym->type = S_OTHER;
 			}
 			if (sym->flags & def_flags) {
-				conf_warning("trying to reassign symbol %s", sym->name);
-				break;
+				conf_warning("override: reassigning to symbol %s", sym->name);
 			}
 			if (conf_set_sym_val(sym, def, def_flags, p))
 				continue;
@@ -297,11 +295,9 @@ load:
 				}
 				break;
 			case yes:
-				if (cs->def[def].tri != no) {
-					conf_warning("%s creates inconsistent choice state", sym->name);
-					cs->flags &= ~def_flags;
-				} else
-					cs->def[def].val = sym;
+				if (cs->def[def].tri != no)
+					conf_warning("override: %s changes choice state", sym->name);
+				cs->def[def].val = sym;
 				break;
 			}
 			cs->def[def].tri = E_OR(cs->def[def].tri, sym->def[def].tri);