libjpeg: add license information

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libjpeg/libjpeg.mk

@@ -7,6 +7,8 @@
 LIBJPEG_VERSION = 8d
 LIBJPEG_SITE = http://www.ijg.org/files/
 LIBJPEG_SOURCE = jpegsrc.v$(LIBJPEG_VERSION).tar.gz
+LIBJPEG_LICENSE = jpeg-license (BSD-3c-like)
+LIBJPEG_LICENSE_FILES = README
 LIBJPEG_INSTALL_STAGING = YES
 
 define LIBJPEG_REMOVE_USELESS_TOOLS