libv4l: needs dynamic library support

Fixes:
http://autobuild.buildroot.net/results/752/752cda64e3a4a73adfd9b383d5f42b61e4a1e641/
http://autobuild.buildroot.net/results/042/0423132222f8a8030f703bb8d755f3e9a4ee73d8/
http://autobuild.buildroot.net/results/908/9087769da17e2092c3ad2eb901ff87c1d6437e6a/



Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>