EDAC/powerpc: Remove PPC_MAPLE drivers

These two drivers are only buildable for the powerpc "maple" platform
(CONFIG_PPC_MAPLE), which has now been removed, see
commit 62f8f307 ("powerpc/64: Remove maple platform").

Remove the drivers.

Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241112084134.411964-1-mpe@ellerman.id.au