uboot-phytec

Fix dependency generation for older gcc versions

 With gcc 3.3.3 at least, compilation fails with

Generating include/autoconf.mk
gcc: compilation of header file requested
make: *** [include/autoconf.mk] Error 1

since commit 16fe77752eee099b9fb61ed73460e51cc94b37ba.

Signed-off-by: Vlad Lungu <vlad@comsys.ro>