OMAP4: Intialize IVA Device in addition to DSP device.

OMAP4 has two different Devices IVA and DSP. DSP is bound
with IVA for DVFS. The registration of IVA dev in API
'omap2_init_processor_devices' was missing. Init dev for
'iva_dev' is added.

This also fixes the following error seen during boot as
omap2_set_init_voltage can now find the iva device

	omap2_set_init_voltage: Invalid parameters!
	omap2_set_init_voltage: Unable to put vdd_iva to its init voltage

Signed-off-by: Shweta Gulati <shweta.gulati@ti.com>
Acked-by: Nishanth Menon <nm@ti.com>