MLBEDSW-2919: bringup: int16 avgpool diff on FPGA

 - Set ACC_FORAMT to 32-bit for pooling operations.

Signed-off-by: Tim Hall <tim.hall@arm.com>
Change-Id: I69ebd08c2db4c5ec966ca13c872c9b0c8330bb6f
diff --git a/ethosu/vela/shared_buffer_allocation.py b/ethosu/vela/shared_buffer_allocation.py
index fdcbe94..0f5c1c8 100644
--- a/ethosu/vela/shared_buffer_allocation.py
+++ b/ethosu/vela/shared_buffer_allocation.py
@@ -84,7 +84,8 @@
             else:
                 self.ifm_depth = ifm_tensor.shape[-1]
             if self.ifm_bits == 16:
-                self.use_accumulator_element = SHRAMElements.Acc40
+                if ps.npu_block_type != NpuBlockType.Pooling:
+                    self.use_accumulator_element = SHRAMElements.Acc40
                 self.use_ifm_element = self.use_ifm_element + 1
                 assert (self.use_ifm_element == SHRAMElements.IFM16) or (
                     self.use_ifm_element == SHRAMElements.IFM16_Elementwise