drm/amd/pm/powerplay/smumgr: Fix PCIeBootLinkLevel value on Iceland

drm/amd/pm/powerplay/smumgr: Fix PCIeBootLinkLevel value on Iceland

Previously this was initialized with zero which represented PCIe Gen
1.0 instead of using the
maximum value from the speed table which is the behaviour of all other
smumgr implementations.

Fixes: 18aafc59b106 ("drm/amd/powerplay: implement fw related smu interface for iceland.")
Signed-off-by: John Smith <itistotalbotnet@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>