docs: net: statistics.rst: remove a duplicated kernel-doc

include/linux/ethtool.h is included twice with kernel-doc,
both to document ethtool_pause_stats(). The first one is
at statistics.rst, and the second one at ethtool-netlink.rst.

Replace one of the references to use the name of the
function. The automarkup.py extension should create the
cross-references.

Solves this warning:

	../Documentation/networking/ethtool-netlink.rst: WARNING: Duplicate C declaration, also defined in 'networking/statistics'.
	Declaration is 'ethtool_pause_stats'.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Link: https://lore.kernel.org/r/fdbf853bbdaf3bc1d38f32744b739d175c5c31f5.1603791716.git.mchehab+huawei@kernel.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/networking/statistics.rst

@@ -175,5 +175,4 @@ The following structures are internal to the kernel, their members are
 translated to netlink attributes when dumped. Drivers must not overwrite
 the statistics they don't report with 0.
 
-.. kernel-doc:: include/linux/ethtool.h
-    :identifiers: ethtool_pause_stats
+- ethtool_pause_stats()