drm/amd/display: Fix conversions between bytes and KB

[Why]
There are a number of instances where we convert HostVMMinPageSize or
GPUVMMinPageSize from bytes to KB by dividing (rather than multiplying) and
vice versa.
Additionally, in some cases, a parameter is passed through DML in KB but
later checked as if it were in bytes.

Cc: stable@vger.kernel.org
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Taimur Hassan <syed.hassan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>