ARM: dts: silk: Fix W=1 dtc warnings

Warning (unit_address_vs_reg): Node /regulator@0 has a unit name, but no reg property
Warning (unit_address_vs_reg): Node /regulator@3 has a unit name, but no reg property
Warning (unit_address_vs_reg): Node /regulator@4 has a unit name, but no reg property

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>