image_types_sparse: fix sparse image generation

After changing image_types_sparse to follow new override syntax, using
this class generates the syntax error, because CONVERSION_CMD:sparse()
function is added to the generated shell file, but color can not be a
part of the function name. Rewrite it to be the variable rather than the
function, so that it does not end up the run.do_image_FOO file.

DEBUG: Executing shell function do_image_ext4
[.......]/temp/run.do_image_ext4.1247938: line 184: `CONVERSION_CMD:sparse': not a valid identifier
WARNING: [.......]/temp/run.do_image_ext4.1247938:151 exit 2 from 'export systemd_user_unitdir="/usr/lib/systemd/user"'
WARNING: Backtrace (BB generated script):
	openembedded#1: main, [.......]/temp/run.do_image_ext4.1247938, line 151
ERROR: Execution of '[.......]/temp/run.do_image_ext4.1247938' failed with exit code 2:
[.......]/temp/run.do_image_ext4.1247938: line 184: `CONVERSION_CMD:sparse': not a valid identifier
WARNING: [.......]/temp/run.do_image_ext4.1247938:151 exit 2 from 'export systemd_user_unitdir="/usr/lib/systemd/user"'
WARNING: Backtrace (BB generated script):
	openembedded#1: main, [.......]/temp/run.do_image_ext4.1247938, line 151

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/classes/image_types_sparse.bbclass

@@ -1,16 +1,16 @@
 inherit image_types
 
 CONVERSIONTYPES += "sparse"
-CONVERSION_CMD:sparse() {
-    in="${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.${type}"
-    out="${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.${type}.sparse"
-    case "${type}" in
-        ext*)
-            ext2simg "$in" "$out"
-            ;;
-        *)
-            img2simg "$in" "$out"
-            ;;
-    esac
-}
+CONVERSION_CMD:sparse = " \
+    case "${type}" in \
+        ext*) \
+            ext2simg "${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.${type}" \
+                     "${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.${type}.sparse" \
+            ;; \
+        *) \
+            img2simg "${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.${type}" \
+                     "${IMAGE_NAME}${IMAGE_NAME_SUFFIX}.${type}.sparse" \
+            ;; \
+    esac \
+"
 CONVERSION_DEPENDS_sparse = "android-tools-native"