kernel-yocto: remove do_shared_workdir from SRCTREECOVEREDTASKS

kernel-yocto: remove do_shared_workdir from SRCTREECOVEREDTASKS

Various recipes depend on the kernel's do_shared_workdir
task, a quick grep suggests all external kernel modules
(via module.bbclass), but also perf, and potentially any
additional headers as outlined in linux-libc-headers.inc
are affected.

Having do_shared_workdir in SRCTREECOVEREDTASKS means this
task is removed when externalsrc is enabled, making all
those recipes fail as the task they depend on,
virtual/kernel:do_shared_workdir, doesn't exist.

Remove do_shared_workdir from SRCTREECOVEREDTASKS so that
all those recipes work even if externalsrc is activated.

According to the comment in here, the reason for
do_shared_workdir to be removed as a task is because it
modifies the source tree, but that doesn't seem to be
case.

(From OE-Core rev: 29e99d7a57803e450920600b5d35c5b4e58a0ede)

Signed-off-by: Andre Draszik <git@andred.net>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>