EDAC/mv64x60: Remove orphan mv64x60 driver

EDAC/mv64x60: Remove orphan mv64x60 driver

The mv64x60 EDAC driver depends on CONFIG_MV64X60. But that symbol is
not user-selectable, and the last code that selected it was removed
with the C2K board support in 2018, see:

  92c8c16f3457 ("powerpc/embedded6xx: Remove C2K board support")

That means the driver is now dead code, so remove it.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20201207040253.628528-1-mpe@ellerman.id.au