EDAC: Fix EDAC Kconfig menu

After f65aad41

("MIPS: Cavium: Add EDAC support."), when entering
the "Device Drivers" toplevel menu in menuconfig, the suboptions behind
EDAC appeared merged with the rest of the device drivers types. This was
because the menuconfig option EDAC is querying an EDAC_SUPPORT Kconfig
bool which was defined after the menu definition.

When pushing EDAC_SUPPORT up, before the menu definition, the variable
is defined earlier and the above menuconfig artifact doesn't happen.

Drop a useless menuconfig comment while at it.

Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Borislav Petkov <bp@alien8.de>