sb_edac: Mark get_mci_for_node_id as static

sb_edac: Mark get_mci_for_node_id as static

This patch marks the function get_mci_for_node_id() as static because it
is not used outside of sb_edac.c.

Thus, it also eliminates the following warning:
drivers/edac/sb_edac.c:918:22: warning: no previous prototype for ‘get_mci_for_node_id’ [-Wmissing-prototypes]

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Link: http://lkml.kernel.org/r/0441f508186fc4eeabc8e9c3e4dde013d99405d4.1387029387.git.rashika.kheria@gmail.com
Signed-off-by: Borislav Petkov <bp@suse.de>