mk: fix pdf doc rules order
mk: fix pdf doc rules order

Re-ordered the guide-pdf-% and guide-% rules to allow
the doc-guides-pdf target to build with make 3.81. It
builds unmodified with all later versions of make.

Fixes: ebf8050afd44 ("doc: add pdf output")

Reported-by: Tetsuya Mukawa <b347a9f5840345582b30d055e1e99ac6ac7bce3c@igel.co.jp>
Signed-off-by: John McNamara <af31595c36a4239b9676e9b3a777d3e2f15a6c4d@intel.com>
Signed-off-by: Thomas Monjalon <ee2fa8b2681c737f775687e475dcbf2028a412f1@6wind.com>

phermansson/dpdk,phermansson/dpdk,phermansson/dpdk,phermansson/dpdk