i915/perf: Do not add ggtt offset to hw_tail

ggtt offset for hw_tail is not required for the calculations, so drop
it.

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230605193923.1836048-3-umesh.nerlige.ramappa@intel.com

drivers/gpu/drm/i915/i915_perf.c

@@ -565,7 +565,7 @@ static bool oa_buffer_check_unlocked(struct i915_perf_stream *stream)
 	partial_report_size %= report_size;
 
 	/* Subtract partial amount off the tail */
-	hw_tail = gtt_offset + OA_TAKEN(hw_tail, partial_report_size);
+	hw_tail = OA_TAKEN(hw_tail, partial_report_size);
 
 	/* NB: The head we observe here might effectively be a little
 	 * out of date. If a read() is in progress, the head could be
@@ -574,7 +574,6 @@ static bool oa_buffer_check_unlocked(struct i915_perf_stream *stream)
 	head = stream->oa_buffer.head - gtt_offset;
 	read_tail = stream->oa_buffer.tail - gtt_offset;
 
-	hw_tail -= gtt_offset;
 	tail = hw_tail;
 
 	/* Walk the stream backward until we find a report with report