drm/amd/display: Covert integers to double before divisions

Integer divisions result in loss of fractional and accuracy is lost
when assigned or compared with double. It is necessary to perform
double/integer instead or explicitly cast them to double.

This fixes 54 UNINTENDED_INTEGER_DIVISION issues reported by Coverity.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>