package/dhcpcd: fix pid path

From the README:
    dhcpcd-9 defaults the run directory to `/var/run/dhcpcd` instead of
    `/var/run` and the prefix of dhcpcd has been removed from the files.

Make it so.

Signed-off-by: Konstantin Menyaev <KAMenyaev@sberdevices.ru>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>