drm/amd/display: Fix possible overflow in integer multiplication

[WHAT & HOW]
Integer multiplies integer may overflow in context that expects an
expression of unsigned/siged long long (64 bits). This can be fixed
by casting integer to unsigned/siged long long to force 64 bits results.

This fixes 26 OVERFLOW_BEFORE_WIDEN issues reported by Coverity.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Jerry Zuo <jerry.zuo@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>