pulseaudio: add dependency on atomic operations

This fixes:
http://autobuild.buildroot.net/results/d463f3bf730a600a07ed6cd33695bf45e9fd3540/



Signed-off-by: Anton Kolesov <Anton.Kolesov@synopsys.com>
[yann.morin.1998@free.fr: use the new symbol; remove comment strings]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>