bcmgenet: constrain max DMA burst length

raspberrypi inclusion
category: feature
bugzilla: 50432

--------------------------------
Signed-off-by: NFang Yafen <yafen@iscas.ac.cn>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/net/ethernet/broadcom/genet/bcmgenet.h

@@ -29,7 +29,7 @@
 #define ENET_PAD		8
 #define ENET_MAX_MTU_SIZE	(ETH_DATA_LEN + ETH_HLEN + VLAN_HLEN + \
 				 ENET_BRCM_TAG_LEN + ETH_FCS_LEN + ENET_PAD)
-#define DMA_MAX_BURST_LENGTH    0x10
+#define DMA_MAX_BURST_LENGTH    0x08
 
 /* misc. configuration */
 #define MAX_NUM_OF_FS_RULES		16