drm/i915: Correct SFC_DONE register offset

drm/i915: Correct SFC_DONE register offset

The register offset for SFC_DONE was missing a '0' at the end, causing
us to read from a non-existent register address.  We only use this
register in error state dumps so the mistake hasn't caused any real
problems, but fixing it will hopefully make the error state dumps a bit
more useful for debugging.

Fixes: e50dbdbfd9fb ("drm/i915/tgl: Add SFC instdone to error state")
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210728233411.2365788-1-matthew.d.roper@intel.com
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>