net: qualcomm: rmnet: Capture all drops in transmit path

Packets in transmit path could potentially be dropped if there were
errors while adding the MAP header or the checksum header.
Increment the tx_drops stats in these cases.

Additionally, refactor the code to free the packet and increment
the tx_drops stat under a single label.

CRs-Fixed: 2226308
Change-Id: I4dd0ef20afbaf13c950d5d645682834e1745cdb9
Signed-off-by: David S. Miller <davem@davemloft.net>
Git-commit: 1eece799d3f611a28a25319aabbccd4ac948098f
Git-repo: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git


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