bridge: mrp: Fix endian conversion and some other warnings

The following sparse warnings are fixed:
net/bridge/br_mrp.c:106:18: warning: incorrect type in assignment (different base types)
net/bridge/br_mrp.c:106:18:    expected unsigned short [usertype]
net/bridge/br_mrp.c:106:18:    got restricted __be16 [usertype]
net/bridge/br_mrp.c:281:23: warning: incorrect type in argument 1 (different modifiers)
net/bridge/br_mrp.c:281:23:    expected struct list_head *entry
net/bridge/br_mrp.c:281:23:    got struct list_head [noderef] *
net/bridge/br_mrp.c:332:28: warning: incorrect type in argument 1 (different modifiers)
net/bridge/br_mrp.c:332:28:    expected struct list_head *new
net/bridge/br_mrp.c:332:28:    got struct list_head [noderef] *
net/bridge/br_mrp.c:332:40: warning: incorrect type in argument 2 (different modifiers)
net/bridge/br_mrp.c:332:40:    expected struct list_head *head
net/bridge/br_mrp.c:332:40:    got struct list_head [noderef] *
net/bridge/br_mrp.c:682:29: warning: incorrect type in argument 1 (different modifiers)
net/bridge/br_mrp.c:682:29:    expected struct list_head const *head
net/bridge/br_mrp.c:682:29:    got struct list_head [noderef] *

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 2f1a11ae ("bridge: mrp: Add MRP interface.")
Fixes: 4b8d7d4c ("bridge: mrp: Extend bridge interface")
Fixes: 9a9f26e8 ("bridge: mrp: Connect MRP API with the switchdev API")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Acked-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>