EDAC/altera: Add separate SDRAM EDAC config

The CONFIG_ALTERA_EDAC Kconfig symbol always enables the SDRAM EDAC
functionality. On the newer architectures, however, there are cases
where the peripheral EDAC functionality is enabled but SDRAM needs to be
disabled.

Move SDRAM functions so they can be contained inside the conditional
CONFIG. Create new CONFIG option just for SDRAM.

 [ bp: Massage commit message. ]

Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: James Morse <james.morse@arm.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: dinguyen@kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: linux@armlinux.org.uk
Link: https://lkml.kernel.org/r/1551121006-4657-2-git-send-email-thor.thayer@linux.intel.com