UPSTREAM: drm/i915/display: Store hw clock for C20

We can calculate the hw port clock during the hw readout
and store it as pll_state->clock for C20 state verification.
In order to do that we need to move intel_c20pll_calc_port_clock()
function.

Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240102115741.118525-3-mika.kahola@intel.com


(cherry picked from commit 172516e1)
Signed-off-by: Lee Shawn C <shawn.c.lee@intel.com>

BUG=b:366539867
TEST=DP-ALT displays should work fine

Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/5875365


Tested-by: Shawn C Lee <shawn.c.lee@intel.com>
Commit-Queue: Shawn C Lee <shawn.c.lee@intel.com>
Reviewed-by: Drew Davenport <ddavenport@chromium.org>
Reviewed-by: Sean Paul <sean@poorly.run>
Change-Id: I22d75686c658352e1ffb54fec70656f6e3475049
Signed-off-by: Hubert Mazur <hmazur@google.com>
Signed-off-by: Tomasz Nowicki <tnowicki@google.com>