mongoose: fix license info

License file is called LICENSE, not COPYING.

Fixes http://autobuild.buildroot.net/results/b45499489abad2a089b47d8470632b4152862c89/build-end.log

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/mongoose/mongoose.mk

@@ -8,7 +8,7 @@ MONGOOSE_VERSION = 3.7
 MONGOOSE_SOURCE = mongoose-$(MONGOOSE_VERSION).tgz
 MONGOOSE_SITE = https://mongoose.googlecode.com/files
 MONGOOSE_LICENSE = MIT
-MONGOOSE_LICENSE_FILES = COPYING
+MONGOOSE_LICENSE_FILES = LICENSE
 
 MONGOOSE_CFLAGS = $(TARGET_CFLAGS) $(TARGET_LDFLAGS)