ar7: remove 972-cpmac_fixup patch

This patch is causing more harm than good on most AR7 routers out there,
better have no manageable switch rather than no ethernet connection, at
least for now.

Fixes #16523, #5927

Signed-off-by: Florian Fainelli <florian@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42168 3c298f89-4303-0410-b956-a3cf2f4a3e73