drm/i915/icl: add ICL support to cnl_set_procmon_ref_values

On ICL we have two sets of registers: one for port A and another for
port B. The set of port A registers is the same as the CNL registers.

Since the procmon table on ICL is the same we want to reuse the CNL
function. To do that we add a port argument and make CNL always call
the function passing port A. This way, we'll be able to easily reuse
the function on ICL when we add icl_display_core_init().

v2: Don't use _PICK() when you can use a ternary operator.
v3: Don't use a ternary operation when you can use _MMIO_PORT (Ville).
    Add an extra comment about why we're passing PORT_A (James).

Reviewed-by: James Ausmus <james.ausmus@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180205154046.11485-2-paulo.r.zanoni@intel.com