OMAP: DSS2: Add new registers for NV12 support

Add new registers specific to UV color component that are introduced in OMAP4.
Add simple helper functions to configure the newly added registers.
These new registers are mainly:
- UV base address registers used specifically for NV12 color-format
- FIR registers used for UV-color-component scaling on OMAP4
- Accumulator registers used for UV-color-component scaling
Add these new registers to save/restore and DUMPREG functions.
Also add two new features for OMAP4:
- FEAT_HANDLE_UV_SEPARATE - this is used on OMAP4 as UV color-component requires
  separate handling.
- FEAT_ATTR2 - this is used on OMAP4 to configure new ATTRIBUTES2 register.

Signed-off-by: Amber Jain <amber@ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>