uboot-phytec

syscon: update syscon_node_to_regmap to use the DM functions

+ Update the function syscon_node_to_regmap() to force bound on
  syscon uclass and directly use the list of device from DM.
+ Remove the static list syscon_list.

This patch avoid issue (crash) when syscon_node_to_regmap() is called
before and after reallocation (list content is invalid).

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>