ARM: dts: Add S5K5BA sensor regulator definitions for Trats board

Add MAX8998 LDO12 and fixed voltage regulator nodes. While at it,
all fixed voltage regulator nodes are grouped in a 'regulators' node.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>