EDAC/highbank: Fix memory leak in highbank_mc_probe()

When devres_open_group() fails, it returns -ENOMEM without freeing memory
allocated by edac_mc_alloc().

Call edac_mc_free() on the error handling path to avoid a memory leak.

  [ bp: Massage commit message. ]

Fixes: a1b01edb

 ("edac: add support for Calxeda highbank memory controller")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Link: https://lore.kernel.org/r/20221229054825.1361993-1-linmq006@gmail.com