openocd: openjtag needs libusb-compat

Since commit 9bdf5926 (package/openocd: depends on libftdi1 instead of
libftdi) the OpenJTAG Programmer can be built without libusb-compat, that is a
dependency of libftdi (but not libftdi1). This breaks the build, because
openjtag.c uses libusb-compat headers. Select BR2_PACKAGE_LIBUSB_COMPAT to fix
this.

Fixes:
http://autobuild.buildroot.net/results/d19/d1969e6df56835568fb908b7f252aec0915d9fa4/
http://autobuild.buildroot.net/results/f06/f06ed6df6138ab399036c397c3f72d33d64fe0a3/
http://autobuild.buildroot.net/results/bd7/bd7f90f3cc1d2b395f9849eb0630c2602a075bf5/


...

Cc: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>