r8169: Revert BQL and xmit_more support.

There are certain regressions which are pointing to
these two commits which we are having a hard time
resolving.  So revert them for now.

Specifically this reverts:

	commit 0bec3b70
	Author: Florian Westphal <fw@strlen.de>
	Date:   Wed Jan 7 10:49:49 2015 +0100

	    r8169: add support for xmit_more

and

	commit 1e918876
	Author: Florian Westphal <fw@strlen.de>
	Date:   Wed Oct 1 13:38:03 2014 +0200

	    r8169: add support for Byte Queue Limits

There were some attempts by Eric Dumazet to address some obvious
problems in the TX flow, to see if they would fix the problems,
but none of them seem to help for the regression reporters.

Signed-off-by: David S. Miller <davem@davemloft.net>