Move the rtc node system-power-controller property from
am335x-boneblack-common.dtsi to am335x-bone-common.dtsi.

am335x-boneblack-common.dtsi is included by am335x-boneblack.dts,
am335x-boneblack-wireless.dts, am335x-sancloud-bbe.dts and
am335x-sancloud-bbe-lite.dts. All of these dts files also include
am335x-bone-common.dtsi and thus will retain the rtc node
system-power-controller property.

am335x-bone-common.dtsi is also included by am335x-bone.dts [1],
am335x-bonegreen.dts [2] and am335x-bonegreen-wireless.dts [3]. These
boards will now have the rtc node system-power-controller property too.
This is valid as they also have PMIC_POWR_EN (ZCZ C6) connected to
PWR_EN on the TPS65217B PMIC.

Based on commit 15c7be47fb7c ("ARM: dts: am335x: Add rtc node as
system-power-controller") by Keerthy in ti-linux-5.4.y branch [4].

[1] https://beagleboard.org/static/beaglebone/BEAGLEBONE_SCHEM_A3.pdf
[2] https://github.com/SeeedDocument/BeagleBone_Green/blob/master/resources/BEAGLEBONE_GREEN_V1.pdf
[3] https://github.com/SeeedDocument/BeagleBone_Green_Wireless/blob/master/resources/BeagleBone_Green%20Wireless_V1.0_SCH_20160314.pdf
[4] git://git.ti.com/ti-linux-kernel/ti-linux-kernel.git

Cc: Jason Kridner <jkridner@beagleboard.org>
Cc: Dave Gerlach <d-gerlach@ti.com>
Cc: Keerthy <j-keerthy@ti.com>
Link: https://lore.kernel.org/linux-omap/20211012191311.879838-1-dfustini@baylibre.com/Suggested-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Drew Fustini <dfustini@baylibre.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>