EDAC/sb_edac: Remove redundant initialization of variable rc

The variable rc is being initialized with a value that is never read, it
is being updated later on. The assignment is redundant and thus remove
it.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20211126221848.1125321-1-colin.i.king@gmail.com