sfc: Do not initialise buffer in efx_alloc_special_buffer()

Currently we initialise the newly allocated buffer to all-1s, which is
important for event queues but not for descriptor queues.  And since
we also do that in efx_nic_init_eventq(), it is completely pointless
to do it here.
Signed-off-by: NBen Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/nic.c

@@ -255,9 +255,6 @@ static int efx_alloc_special_buffer(struct efx_nic *efx,
 	buffer->entries = len / EFX_BUF_SIZE;
 	BUG_ON(buffer->dma_addr & (EFX_BUF_SIZE - 1));
 
-	/* All zeros is a potentially valid event so memset to 0xff */
-	memset(buffer->addr, 0xff, len);
-
 	/* Select new buffer ID */
 	buffer->index = efx->next_buffer_table;
 	efx->next_buffer_table += buffer->entries;