baresip: fix recursive dependency

baresip: fix recursive dependency

Since OpenWrt commit e82a4d9cfb ("config: regenerate *_shipped sources")
a few recursive dependencies have been discovered that were not visible
before.

$ make menuconfig
tmp/.config-package.in:103098:error: recursive dependency detected!
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
tmp/.config-package.in:103098: symbol PACKAGE_baresip-mod-pulse depends on PACKAGE_baresip-mod-pulse
tmp/.config-package.in:121863:error: recursive dependency detected!
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
tmp/.config-package.in:121863: symbol PACKAGE_pulseaudio-profiles depends on PACKAGE_pulseaudio-profiles
tmp/.config-package.in:121878:error: recursive dependency detected!
For a resolution refer to Documentation/kbuild/kconfig-language.txt
subsection "Kconfig recursive dependency limitations"
tmp/.config-package.in:121878: symbol PACKAGE_pulseaudio-tools depends on PACKAGE_pulseaudio-tools

The recursive dependencies were reported at [1] and [2].

This commit addresses the recursive dependency of baresip-mod-pulse. The
new dependency string may look a bit peculiar, but it works and when
specified like this pulseaudio (when selected) doesn't get compiled
automatically when the intention is only to build baresip with mod-pulse
disabled (which in general is why we have the "patsubst" in the module
builder - but this is only triggered when the dependency has a leading
"+").

[1] https://github.com/openwrt/packages/issues/9300
[2] https://forum.openwrt.org/t/make-menuconfig-errors-this-day/38673/5

Signed-off-by: Sebastian Kemper <sebastian_ml@gmx.net>