This worked before by coincidence, as the regulator was probed and enabled
before PCI RC probe. But probe order changed since commit 259b93b2
("regulator: Set PROBE_PREFER_ASYNCHRONOUS for drivers that existed in
4.14") and PCIe supply is enabled after RC.
Fix this by adding the regulator to RC node.

The PCIe vaux regulator still needs to be enabled unconditionally for
Mini-PCIe USB-only devices.

Fixes: ef384624 ("ARM: dts: imx6qdl: add TQ-Systems MBa6x device trees")
Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>