jpeg-turbo: add license details

- jpeg-turbo is covered by 3 licenses: IJG (libjpeg),
  BSD-3-Clause (TurboJPEG) and Zlib (SIMD)
- Add README.ijg
- Add hash for license files

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit ca668476b3aa0ce42e7ffb79f484c5eadbcc99d2)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/jpeg-turbo/jpeg-turbo.hash

@@ -3,3 +3,5 @@ sha1 e788f6defa58b4393a5e1685c018f3b962971457  libjpeg-turbo-1.5.2.tar.gz
 md5 6b4923e297a7eaa255f08511017a8818  libjpeg-turbo-1.5.2.tar.gz
 # Locally computed
 sha256 9098943b270388727ae61de82adec73cf9f0dbb240b3bc8b172595ebf405b528  libjpeg-turbo-1.5.2.tar.gz
+sha256 5c08657eda60b7946a913ee22ac73603335a468a6aa95204506a1586a8d677ee  LICENSE.md
+sha256 53a3e3c299e08856964f4c5986e242c3695837b73c64625092f70c774e8af5d2  README.ijg

package/jpeg-turbo/jpeg-turbo.mk

@@ -7,8 +7,8 @@
 JPEG_TURBO_VERSION = 1.5.2
 JPEG_TURBO_SOURCE = libjpeg-turbo-$(JPEG_TURBO_VERSION).tar.gz
 JPEG_TURBO_SITE = https://downloads.sourceforge.net/project/libjpeg-turbo/$(JPEG_TURBO_VERSION)
-JPEG_TURBO_LICENSE = jpeg-license (BSD-3-Clause-like)
-JPEG_TURBO_LICENSE_FILES = LICENSE.md
+JPEG_TURBO_LICENSE = IJG (libjpeg), BSD-3-Clause (TurboJPEG), Zlib (SIMD)
+JPEG_TURBO_LICENSE_FILES = LICENSE.md README.ijg
 JPEG_TURBO_INSTALL_STAGING = YES
 JPEG_TURBO_PROVIDES = jpeg
 JPEG_TURBO_DEPENDENCIES = host-pkgconf