sstate-cache-management.sh:fix the incorrect usage of option `-d'

The description of option `-d' is not correct in useage. It is used to
remove duplicate and debug at the same time. Use option `-D' to control
debug info output and the option `-d' to flag remove duplicate.

[YOCTO #3635]

(From OE-Core rev: fa0b40c233e757fe986aa45798b35b60b89c879f)

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/sstate-cache-management.sh

@@ -72,7 +72,7 @@ Options:
   -v, --verbose
         explain what is being done
 
-  -d, --debug
+  -D, --debug
         show debug info, repeat for more debug info
 
 EOF
@@ -388,7 +388,7 @@ while [ -n "$1" ]; do
       verbose="-v"
       shift
         ;;
-    --debug)
+    --debug|-D)
       debug=`expr $debug + 1`
       echo "Debug level $debug"
       shift