package/dvb-apps: is not parallel-safe

This is invisible because the timings make it excessively difficult to
hit, but the Makefile is inherently flawed for parallel build, as it
contains:

    $(objects): atsc_psip_section.c atsc_psip_section.h

    atsc_psip_section.c atsc_psip_section.h:
        perl section_generate.pl atsc_psip_section.pl

and the perl script section_generate.pl will create both the .c and .h
files in one go, but given the construct above, there can be two such
script that run in parallel, which can clobber the generated .c and/or
.h files.

So, make dvb-apps a MAKE1 package.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>