net: qualcomm: rmnet: Fix incorrect UL checksum offload logic

The udp_ip4_ind bit is set only for IPv4 UDP non-fragmented packets
so that the hardware can flip the checksum to 0xFFFF if the computed
checksum is 0 per RFC768.

However, this bit had to be set for IPv6 UDP non fragmented packets
as well per hardware requirements. Otherwise, IPv6 UDP packets
with computed checksum as 0 were transmitted by hardware and were
dropped in the network.

In addition to setting this bit for IPv6 UDP, the field is also
appropriately renamed to udp_ind as part of this change.

Change-Id: I3f4ee599e2a9d42e71ee1f4dc717668960168602
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>