drm/amdgpu/virt: remove redundant variable pf2vf_ver

Variable pf2vf_ver is assigned but never read, it is redundant and
hence can be removed.

Cleans up clang warning:
drivers/gpu/drm/amd/amdgpu/amdgpu_virt.c:310:3: warning: Value stored
to 'pf2vf_ver' is never read

Reivewed-by: Horace Chen <horace.chen@amd.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>