This reverts commit 746f0770f916e6c48e422d6a34e67eae16707f0e.
Now that we can register a SoC specific regmap with syscon using
of_syscon_register_regmap() api we can switch back to using
syscon_regmap_lookup_by_phandle() in the client drivers.
Signed-off-by: Peter Griffin <peter.griffin@xxxxxxxxxx>