x86/ras: Fix build warnings in <linux/aer.h>

Fix build warning due to a missing forward declaration in
<linux/aer.h>.  We need struct pci_dev to be forward declared so we
can define pointers to it, but we don't need to pull in the whole
definition.

build log:

In file included from include/ras/ras_event.h:11:0,
                 from drivers/ras/ras.c:13:
include/linux/aer.h:42:129: warning: ‘struct pci_dev’
declared inside parameter list [enabled by default]

include/linux/aer.h:42:129: warning: its scope is only
this definition or declaration, which is probably not
what you want [enabled by default]

include/linux/aer.h:46:130: warning: ‘struct pci_dev’
declared inside parameter list [enabled by default]

include/linux/aer.h:50:136: warning: ‘struct pci_dev’
declared inside parameter list [enabled by default]

include/linux/aer.h:57:14: warning: ‘struct pci_dev’
declared inside parameter list [enabled by default]

Signed-off-by: Mike Qiu <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Acked-by: Randy Dunlap <[email protected]>
Tested-by: Randy Dunlap <[email protected]>
Acked-by: Bjorn Helgaas <[email protected]>
Signed-off-by: Tony Luck <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>

include/linux/aer.h

@@ -11,6 +11,8 @@
 #define AER_FATAL			1
 #define AER_CORRECTABLE			2
 
+struct pci_dev;
+
 struct aer_header_log_regs {
 	unsigned int dw0;
 	unsigned int dw1;