mwifiex: support wowlan magic-packet encapsulated as UDP packet

When magic-packet is generated as a UDP packet the offset should
be 20+8 more bytes to cover IPv4 header and UDP header. So the
total offset become 56.
Add a new MEF entry to support both magic-packet patterns
generated by different tools.

Cc: Andreas Fenkart <afenkart@gmail.com>
Signed-off-by: Zhiyuan Yang <yangzy@marvell.com>
Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>