OMAP2, 3: DSS2: Use Regulator init with driver name

Use driver name in regulator inits needed for display instead of using device
structure name.

Reviewed-by: Kevin Hilman <khilman@ti.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Senthilvadivu Guruswamy <svadivu@ti.com>
Signed-off-by: Sumit Semwal <sumit.semwal@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>