drm/msm/dsi: fix 32-bit signed integer extension in pclk_rate calculation

drm/msm/dsi: fix 32-bit signed integer extension in pclk_rate calculation

When (mode->clock * 1000) is larger than (1<<31), int to unsigned long
conversion will sign extend the int to 64 bits and the pclk_rate value
will be incorrect.

Fix this by making the result of the multiplication unsigned.

Note that above (1<<32) would still be broken and require more changes, but
its unlikely anyone will need that anytime soon.

Fixes: c4d8cfe516dc ("drm/msm/dsi: add implementation for helper functions")
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/618434/
Link: https://lore.kernel.org/r/20241007050157.26855-2-jonathan@marek.ca
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>