ecryptfs: remove unnecessary d_drop calls in ecryptfs_link

Unnecessary because it would unhash perfectly valid dentries, causing them
to have to be re-looked up the next time they're needed, which presumably is
right after.

Signed-off-by: Aseem Rastogi <arastogi@cs.sunysb.edu>
Signed-off-by: Shrikar archak <shrikar84@gmail.com>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Cc: Saumitra Bhanage <sbhanage@cs.sunysb.edu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>