xfs/libxfs: replace kmalloc() and memcpy() with kmemdup()

xfs/libxfs: replace kmalloc() and memcpy() with kmemdup()

The source static analysis tool gave the following advice:

./fs/xfs/libxfs/xfs_dir2.c:382:15-22: WARNING opportunity for kmemdup

 → 382         args->value = kmalloc(len,
   383                          GFP_KERNEL | __GFP_NOLOCKDEP | __GFP_RETRY_MAYFAIL);
   384         if (!args->value)
   385                 return -ENOMEM;
   386
 → 387         memcpy(args->value, name, len);
   388         args->valuelen = len;
   389         return -EEXIST;

Replacing kmalloc() + memcpy() with kmemdump() doesn't change semantics.
Original code works without fault, so this is not a bug fix but proposed improvement.

Link: https://lwn.net/Articles/198928/
Fixes: 94a69db2367ef ("xfs: use __GFP_NOLOCKDEP instead of GFP_NOFS")
Fixes: 384f3ced07efd ("[XFS] Return case-insensitive match for dentry cache")
Fixes: 2451337dd0439 ("xfs: global error sign conversion")
Cc: Carlos Maiolino <cem@kernel.org>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Chandan Babu R <chandanbabu@kernel.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: linux-xfs@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Mirsad Todorovac <mtodorovac69@gmail.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>