sdhci: fdt: Always try to get the phy and the syscon

Per the bindings the phy and the syscon can always be present not just
for RK3399.

Reviewed-by: bz
Differiential Revision: https://reviews.freebsd.org/D41809
Sponsored by: Beckhoff Automation GmbH & Co. KG

(cherry picked from commit 0ee5d6fcfc63be48fd7c1b461917dfb880dc7f72)