rdma: Add print of link CapabilityMask2 flags

rdma: Add print of link CapabilityMask2 flags

CapabilityMask2 is defined in IBTA spec as a member of PortInfo.
Add translation to string of new CapabilityMask2 expansion of link caps.

The flags are concatenated to current caps print as seen in this example
printing EXT_INFO flag:

root@server-22 $ rdma -d link
1/1: mlx5_0/1: subnet_prefix fe80:0000:0000:0000 lid 2 sm_lid 2 lmc 0
	state ACTIVE physical_state LINK_UP
caps: <SM, TRAP, SL_MAP, SYS_IMAGE_GUID, CABLE_INFO, EXTENDED_SPEEDS,
	CAP_MASK2, CM, DEVICE_MGMT, VENDOR_CLASS, CAP_MASK_NOTICE,
	CLIENT_REG, OTHER_LOCAL_CHANGES, MULT_PKER_TRAP, EXT_INFO>

Signed-off-by: Michael Guralnik <michaelgur@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: David Ahern <dsahern@gmail.com>