drm/amd/display: Add check for granularity in dml ceil/floor helpers

In the Linux kernel, the following vulnerability has been resolved:

drm/amd/display: Add check for granularity in dml ceil/floor helpers

[Why]

Wrapper functions for dcn_bw_ceil2() and dcn_bw_floor2()

should check for granularity is non zero to avoid assert and

divide-by-zero error in dcn_bw_ functions.

[How]

Add check for granularity 0.

(cherry picked from commit f6e09701c3eb2ccb8cb0518e0b67f1c69742a4ec)