linux: bump default to version 4.16

Added host-bison and host-flex as dependencies after upstream removed
pre-generated files and switched over to build-time generation, for
details see:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=033dba2ec06c47a9fe1b190bc3281058fb20738d
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=29c833061c1d8c2d1d23a62e7061561eadd76cdb



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Tested-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>