RAS/CEC: Fix cec_init() prototype

late_initcall() expects a function that returns an integer. Update the
function signature to match.

 [ bp: Massage commit message into proper sentences. ]

Fixes: 9554bfe4 ("x86/mce: Convert the CEC to use the MCE notifier")
Signed-off-by: Luca Stefani <luca.stefani.ge1@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lkml.kernel.org/r/20200805095708.83939-1-luca.stefani.ge1@gmail.com