Revert "net: Rename mono_delivery_time to tstamp_type for scalabilty"

This reverts commit 8dde0222 which is
commit 4d25ca2d upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Ibbbf947cdc47fad644f5a8fc306659c11930c426
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>