Revert "net: more accurate skb truesize"

Causing low throughput on WLAN data.

This reverts commit 937369a08f1c798e3e46a80a6b80b113718a09d3.

Change-Id: I6cc0145fc3636fa4ae60305662feadd6d474f25b
Signed-off-by: Sridhar Ancha <sancha@codeaurora.org>