drm/amd/display: Remove redundant initialization of variable result

The variable result is being initialized with a value that is never
read, it is being updated immediately afterwards in both branches
of an if statement. The assignment is redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>