Remove the / at the end of PRODUCT_COPY_FILES

Change-Id: Iaef1f002ab8526a1e379029231b75cd6ee40870e

Heya-
    Currently using only your repos/manifests for CyanogenMod 11 for the Kobe (with occasional pulls from upstream for android_packages_apps_Settings that are reverted whenever you merge CyanogenMod/android_packages_apps_Settings into your repo), but noticed that kobe.mk in android_device_moto_mb520 (cm-11.0) had an extra / at the end of PRODUCT_COPY_FILES, which broke build.  I assume the system/bootmenu/2nd-boot/devtree is the last included file, but I wasn't totally certain, so be sure to check before you merge (or if you were to fix it in your own commit, that's fine too).  Thanks, and keep up the good work!

        -Robin K.