Cleaning up git tree from memd_creation.pl

The memd_creation.pl script creates a temporary file in the buildroot
submodule and not cleaned up. This results in a dirty tree and gross
version strings. This commit removes the temporary file from the git
tree.

Resolves open-power/op-build/#1729

Change-Id: Ica28c61ab10455e8546ab6896775c46ab82dcd0b
Reviewed-on: http://ralgit01.raleigh.ibm.com/gerrit1/51678
Reviewed-by: Daniel M. Crowell <dcrowell@us.ibm.com>
Tested-by: Daniel M. Crowell <dcrowell@us.ibm.com>

src/build/buildpnor/memd_creation.pl

@@ -6,7 +6,7 @@
 #
 # OpenPOWER HostBoot Project
 #
-# Contributors Listed Below - COPYRIGHT 2017
+# Contributors Listed Below - COPYRIGHT 2017,2018
 # [+] International Business Machines Corp.
 #
 #
@@ -143,6 +143,7 @@
     }
     close $in_file;
     $offset = $offset + ($max_file_size * ROUNDING_DIVISOR);
+    unlink $new_file;
 }