l2test: Add support to BT_PHY

l2test: Add support to BT_PHY

This makes l2test attempt to read BT_PHY socket option and print out
the supported packet types/PHY:

l2test[7282]: Connected to XX:XX:XX:XX:XX:XX (bredr, psm 4113, dcid 64)
l2test[7282]: Local device XX:XX:XX:XX:XX:XX (bredr, psm 4113, scid 64)
l2test[7282]: Options [imtu 672, omtu 672, flush_to 65535, mode 0, handle 256, class 0x000000, priority 0, rcvbuf 212992]
l2test[7282]: Supported PHY: 0x000001ff
          BR1M1SLOT
          BR1M3SLOT
          BR1M5SLOT
          EDR2M1SLOT
          EDR2M3SLOT
          EDR2M5SLOT
          EDR3M1SLOT
          EDR3M3SLOT
          EDR3M5SLOT

Signed-off-by: Anuj Jain <anuj01.jain@samsung.com>
Signed-off-by: Ayush Garg <ayush.garg@samsung.com>