Fix the following -Wunused-but-set-variable warning:

  drivers/edac/aspeed_edac.c: In function aspeed_probe:
  drivers/edac/aspeed_edac.c:284:22: warning: variable np set but not used [-Wunused-but-set-variable]

It is never used and can be removed.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Stefan Schaeckeler <sschaeck@cisco.com>
Cc: James Morse <james.morse@arm.com>
Cc: Joel Stanley <joel@jms.id.au>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-aspeed@lists.ozlabs.org
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Link: https://lkml.kernel.org/r/20190525144153.2028-1-yuehaibing@huawei.com