drm/amdgpu/swsmu: fix is_support_sw_smu() for VEGA20

VEGA20 is 11.0.2, but it's handled by powerplay, not
swsmu.

Fixes: a8967967 ("drm/amdgpu/amdgpu_smu: convert to IP version checking")
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>