ARM: dts: omap3-igep0020: name twl4030 VPLL2 regulator as vdds_dsi

On Device Tree boot the VDDS_DSI regulator is not linked to
the DPI device so omapfb driver probing fails with:

[    3.186035] OMAPFB: omapfb_probe
[    3.190704] omapdss DPI error: can't get VDDS_DSI regulator
[    3.196594] omapfb omapfb: failed to connect default display
[    3.202667] omapfb omapfb: failed to init overlay connections
[    3.208892] OMAPFB: free_resources
[    3.212493] OMAPFB: free all fbmem
[    3.216735] omapfb omapfb: failed to setup omapfb

As a workaround name the VPLL2 regulator from twl4030 as vdds_dsi
so getting the VDDS_DSI regulator will succeed on dpi_init_regulator().
Signed-off-by: NJavier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: NTony Lindgren <tony@atomide.com>

arch/arm/boot/dts/omap3-igep0020.dts

@@ -215,3 +215,8 @@
 &usbhsehci {
 	phys = <&hsusb1_phy>;
 };
+
+&vpll2 {
+        /* Needed for DSS */
+        regulator-name = "vdds_dsi";
+};