pulseaudio: remove spurious cd in do_compile_prepend

pulseaudio: remove spurious cd in do_compile_prepend

This prepend was cding to ${S}, which then breaks base_do_compile as it assumes
it's in ${B}.  The cd is pointless as all of the operations use absolute paths,
so remove it.

The result of this was that base_do_compile was failing to find the makefiles,
so the compilation happened in do_install.

(From OE-Core rev: ac3a8ce0b672d1488c9074bde1a1d062e0c5fd33)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>