drm/i915/vlv: Rename VLV DPIO register to be more structure to match configdb document.

Some VLV PHY/PLL DPIO registers have group/lane/channel access.  Current
DPIO register definition doesn't have a structure way to break them
down. As a result it is not easy to match the PHY/PLL registers with the
configdb document.  Rename those registers based on the configdb for easy
cross references, and without the need to check the offset in the header
file.

New format is as following.

<platform name>_<DPIO component><optional lane #>_DW<dword # in the
doc>_<optional channel #>

For example,

VLV_PCS_DW0 - Group access to PCS for lane 0 to 3 for PCS DWORD 0.
VLV_PCS01_DW0_CH0 - PCS access to lane 0/1, channel 0 for PCS DWORD 0.

Another example is

VLV_TX_DW0 - Group access to TX lane 0 to 3 for TX DWORD 0
VLV_TX0_DW0 - Refer to TX Lane 0 access only for TX DWORD 0.

There is no functional change on this patch.

v2: Rebase based on previous patch change.
v3: There may be configdb different version that document the start DW
differently. Add a comment to clarify.  Fix up some mismatch start DW
for second PLL block. (Ville)

Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Chon Ming Lee <chon.ming.lee@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>