drm/amdgpu: update type of buf size to u32 for eeprom functions

[ Upstream commit 2aadb520bfacec12527effce3566f8df55e5d08e ]

Avoid overflow issue.

Signed-off-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Yang Wang <kevinyang.wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>