drm/i915: Fix possible int overflow in skl_ddi_calculate_wrpll()

On the off chance that clock value ends up being too high (by means
of skl_ddi_calculate_wrpll() having been called with big enough
value of crtc_state->port_clock * 1000), one possible consequence
may be that the result will not be able to fit into signed int.

Fix this issue by moving conversion of clock parameter from kHz to Hz
into the body of skl_ddi_calculate_wrpll(), as well as casting the
same parameter to u64 type while calculating the value for AFE clock.
This both mitigates the overflow problem and avoids possible erroneous
integer promotion mishaps.

Found by Linux Verification Center (linuxtesting.org) with static
analysis tool SVACE.

Fixes: 82d35437

 ("drm/i915/skl: Implementation of SKL DPLL programming")
Cc: stable@vger.kernel.org
Signed-off-by: Nikita Zhandarovich <n.zhandarovich@fintech.ru>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240729174035.25727-1-n.zhandarovich@fintech.ru
(cherry picked from commit 833cf128

)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>