fsl-eula-unpack: fix deploying EULA

If a recipe, which uses the fsl-eula-unpack bbclass, defines the
variable LIC_FILES_CHKSUM like

    LIC_FILES_CHKSUM = "[...]"

(not using "+=") the content of ${FSL_EULA_FILE}, which is added in
fsl-eula-unpack, is overwritten. So the EULA isn't deployed to the
${LICENSE_DIRECTORY}.

Using 'LIC_FILES_CHKSUM_append' should work in any cases.

Signed-off-by: Stefan Christ <s.christ@phytec.de>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>

meta-fsl-arm/classes/fsl-eula-unpack.bbclass

@@ -6,7 +6,7 @@
 #
 #  SRC_URI = "${FSL_MIRROR}/firmware-imx-${PV};fsl-eula=true"
 
-LIC_FILES_CHKSUM += "file://${FSL_EULA_FILE};md5=acdb807ac7275fe32f9f64992e111241"
+LIC_FILES_CHKSUM_append = " file://${FSL_EULA_FILE};md5=acdb807ac7275fe32f9f64992e111241"
 LIC_FILES_CHKSUM[vardepsexclude] += "FSL_EULA_FILE"
 
 python fsl_bin_do_unpack() {