drm/amdgpu: fix out of bounds access in gfx11 during ip dump

During ip dump in gfx11 the index variable is reused but is
not reinitialized to 0 and this causes the index calculation
to be wrong and access out of bound access.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>