staging: octeon: check request_irq() return value

request_irq() may fail, if so propagate error code.

Signed-off-by: Kulikov Vasiliy <segooon@gmail.com>
Acked-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>