systemd: remove ${PN}-xorg-xinitrc

systemd: remove ${PN}-xorg-xinitrc

In 50-systemd-user.sh which is packaged to sub-package
${PN}-xorg-xinitrc, it exports environment variables DISPLAY and
XAUTHORITY to systemd. It fails to start systemd services which require
these environment variables such as thunar.service:

root@qemux86-64:~# systemctl --user status thunar
● thunar.service - Thunar file manager
Loaded: loaded (/usr/lib/systemd/user/thunar.service; disabled; vendor preset: enabled)
Active: inactive (dead)
Docs: man:Thunar(1)

Nov 14 07:47:29 qemux86-64 systemd[352]: Starting Thunar file manager...
Nov 14 07:47:29 qemux86-64 Thunar[873]: cannot open display:
Nov 14 07:47:29 qemux86-64 systemd[352]: thunar.service: Main process exited, code=exited, status=1/FAILURE
Nov 14 07:47:29 qemux86-64 systemd[352]: thunar.service: Failed with result 'exit-code'.
Nov 14 07:47:29 qemux86-64 systemd[352]: Failed to start Thunar file manager.

It is not convenient to make all such kind of packages require package
${PN}-xorg-xinitrc, so remove the sub-package and merge the only file
provided by it to main package.

No recipe depends on ${PN}-xorg-xinitrc in oe-core and meta-openembedded
now, so no need to set rprovides for it.

Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>