drm/amd/display: Fix uninitialized variable usage in core_link_ 'read_dpcd() & write_...

drm/amd/display: Fix uninitialized variable usage in core_link_ 'read_dpcd() & write_dpcd()' functions

The 'status' variable in 'core_link_read_dpcd()' &
'core_link_write_dpcd()' was uninitialized.

Thus, initializing 'status' variable to 'DC_ERROR_UNEXPECTED' by default.

Fixes the below:
drivers/gpu/drm/amd/amdgpu/../display/dc/link/protocols/link_dpcd.c:226 core_link_read_dpcd() error: uninitialized symbol 'status'.
drivers/gpu/drm/amd/amdgpu/../display/dc/link/protocols/link_dpcd.c:248 core_link_write_dpcd() error: uninitialized symbol 'status'.

Cc: stable@vger.kernel.org
Cc: Jerry Zuo <jerry.zuo@amd.com>
Cc: Jun Lei <Jun.Lei@amd.com>
Cc: Wayne Lin <Wayne.Lin@amd.com>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>