rasdaemon: Fix build warnings unused variable if AMP RAS errors is not enabled

rasdaemon: Fix build warnings unused variable if AMP RAS errors is not enabled

This patch fixes following build warnings unused variable if AMP RAS errors
is not enabled(--enable-amp-ns-decode).

==================================================
ras-aer-handler.c: In function ‘ras_aer_event_handler’:
ras-aer-handler.c:72:21: warning: unused variable ‘fn’ [-Wunused-variable]
  int seg, bus, dev, fn;
                     ^~
ras-aer-handler.c:72:16: warning: unused variable ‘dev’ [-Wunused-variable]
  int seg, bus, dev, fn;
                ^~~
ras-aer-handler.c:72:11: warning: unused variable ‘bus’ [-Wunused-variable]
  int seg, bus, dev, fn;
           ^~~
ras-aer-handler.c:72:6: warning: unused variable ‘seg’ [-Wunused-variable]
  int seg, bus, dev, fn;
      ^~~
ras-aer-handler.c:71:10: warning: variable ‘sel_data’ set but not used [-Wunused-but-set-variable]
  uint8_t sel_data[5];
          ^~~~~~~~
ras-aer-handler.c:70:7: warning: unused variable ‘ipmi_add_sel’ [-Wunused-variable]
  char ipmi_add_sel[105];
       ^~~~~~~~~~~~
==================================================

Signed-off-by: Shiju Jose <shiju.jose@huawei.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>