drm/i915/tgl+: Sanitize DKL PHY register definitions

Not all Dekel PHY registers have a lane instance, so having to specify
this when using them is awkward. It makes more sense to define each PHY
register with its full internal PHY offset where bits 15:12 is the lane
for lane-instanced PHY registers and just a register bank index for other
PHY registers. This way lane-instanced registers can be referred to with
the (tc_port, lane) parameters, while other registers just with a tc_port
parameter.

An additional benefit of this change is to prevent passing a Dekel
register to a generic MMIO access function or vice versa.

v2:
- Fix parameter	reuse in the DKL_REG_MMIO definition.
v3:
- Rebase on latest patchset version.

Cc: Jani Nikula <jani.nikula@intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221025114457.2191004-3-imre.deak@intel.com