meta-rcar-gen3: fix rc.pvr weston dependency

meta-rcar-gen3: fix rc.pvr weston dependency

Add a do_install_append to fix rc.pvr systemd unit weston dependency,
it needs to be weston@.service to work with YP dunfell / 3.1.

Bug-AGL: SPEC-3380, SPEC-3443

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I5f2a6d858c09812ab06e7a1a572fdd96801a8269
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/25012
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-boot-test: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
Reviewed-by: Stéphane Desneux <stephane.desneux@iot.bzh>