drm/amdgpu/tonga: don't call smu_init on resume

smu_init allocates buffers and initializes them.  It does not
touch the hw.  There is no need to do it again on resume.  It
should really be part of sw_init (and smu_fini should be part
of sw_fini), but we need the firmware sizes from the other IPs
for firmware loading so we have to wait until sw init is done
for all other IPs.

Reviewed-by: Sonny Jiang <Sonny.Jiang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>