drm/i915/cnl: Map VBT DDC Pin to BSpec DDC Pin.

drm/i915/cnl: Map VBT DDC Pin to BSpec DDC Pin.

Starting on CNL we now need to map VBT DDC Pin to
BSPec DDC Pin values. Not a direct translation anymore.

According to VBT
Block 2 (General Bytes Definition)
DDC Bus

+----------+-----------+--------------------+
| DDI Type | VBT Value | Bspec Mapped Value |
+----------+-----------+--------------------+
| DDI-B    | 0x1       | 0x1                |
| DDI-C    | 0x2       | 0x2                |
| DDI-D    | 0x3       | 0x4                |
| DDI-F    | 0x4       | 0x3                |
+----------+-----------+--------------------+

v2: Move defines to a better place.
    This is actually CNL_PCH not CNL only.
v3: Accepting Ville's suggestions: enums and array to
    to make this future proof.
v4: Protect the array access as Ville suggested.
    Also accepting all Jani's suggestions:
    	      - use already defined gmbus pin definitions.
	      - use map_ddc_pin for disambiguation.
	      - Add /* sic */ comment on inverted values
	      	so people can easily see it it nos a mistake
		we have the map 3 -> 4 and 4 -> 3 :/

Cc: Jani Nikula <[email protected]>
Cc: Paulo Zanoni <[email protected]>
Cc: Anusha Srivatsa <[email protected]>
Cc: Clinton Taylor <[email protected]>
Cc: Ville Syrjälä <[email protected]>
Signed-off-by: Rodrigo Vivi <[email protected]>
Reviewed-by: Ville Syrjälä <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]