drm/amdgpu: enlarge the VBIOS binary size limit

[ Upstream commit 667b9613 ]

Some chips have a larger VBIOS file so raise the size limit to support
the flashing tool.

Signed-off-by: Shiwu Zhang <shiwu.zhang@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>