package/pulseaudio: fix build-dependency on gettext

In its Config.in, pulseaudio declares a dependency on gettext
using the documented construct:
    select BR2_PACKAGE_GETTEXT if BR2_NEEDS_GETTEXT

but in its .mk file, declares a dependency on the package:
    PULSEAUDIO_DEPENDENCIES = [...] $(if $(BR2_PACKAGE_GETTEXT),gettext) [...]

instead of the documented:
    $(if $(BR2_NEEDS_GETTEXT),gettext)

Fix that.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Tested-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
CC: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>