edac, highbank: Improve and unify naming

Assinging correct names of the 'hb_mc_edac' and 'hb_l2_edac' edac
modules for module, controller and device. Reported values for
Highbank in dmesg are now:

 EDAC MC0: Giving out device to module hb_mc_edac controller
 calxeda,hb-ddr-ctrl: DEV fff00000.memory-controller (INTERRUPT)

 EDAC DEVICE0: Giving out device to module hb_l2_edac controller
 calxeda,hb-sregs-l2-ecc: DEV fff3c200.sregs (INTERRUPT)

Signed-off-by: Robert Richter <robert.richter@linaro.org>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Robert Richter <rric@kernel.org>