graph-depends: support calling from recursive make

The graph-depends script calls make. If the outer make was called
recursively, or if it was called with '-C <somedir>', then the
environment will contain "MAKEFLAGS=w --". Therefore, the recursive
make prints 'Entering' and 'Leaving' messages, which clobbers the
output for dot.

To avoid this, add "--no-print-directory" to the recursive make
arguments. Since we require GNU make 3.81, we can be sure that this
option is available.

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>