edac: arm64: Create a commandline option to disable panic on CE

Currently, the decision to control panic on a correctable error is
through a defconfig. Add a commandline parameter for easy toggling of
this particular option. Also, to make these correctable errors stand-out
in the logs, add a WARN when the panic_on_ce is disabled.

Change-Id: Ie3c61cad2489b680f51d466c8243ba23ccf5375c
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>