serial: kgdb_nmi: remove redundant initialization of variable c

The variable c is being initialized with a value that is never
read, it is being updated later on. The assignment is redundant and
can be removed.

Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Addresses-Coverity: ("Unused value")
Link: https://lore.kernel.org/r/20210513230224.138859-1-colin.king@canonical.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>