Make detect_scsi_host_caps a function on all architectures

In the non linux case some callers like gather_scsi_host_caps needed the
return code of -1 while others like update_caps needed an empty
statement (to avoid a "statement without effect" warning). This is much
simpler solved by using a function instead of a define.
(cherry picked from commit 58662f4416)

src/node_device/node_device_driver.h

@@ -51,16 +51,7 @@ void nodeDeviceUnlock(virNodeDeviceDriverStatePtr driver);
 
 int nodedevRegister(void);
 
-# ifdef __linux__
+int detect_scsi_host_caps(union _virNodeDevCapData *d);
-
-#  define detect_scsi_host_caps(d) detect_scsi_host_caps_linux(d)
-int detect_scsi_host_caps_linux(union _virNodeDevCapData *d);
-
-# else  /* __linux__ */
-
-#  define detect_scsi_host_caps(d)                      (-1)
-
-# endif /* __linux__ */
 
 int nodeNumOfDevices(virConnectPtr conn, const char *cap, unsigned int flags);
 int nodeListDevices(virConnectPtr conn, const char *cap, char **const names,

src/node_device/node_device_linux_sysfs.c

@@ -38,7 +38,7 @@
 #ifdef __linux__
 
 int
-detect_scsi_host_caps_linux(union _virNodeDevCapData *d)
+detect_scsi_host_caps(union _virNodeDevCapData *d)
 {
     char *max_vports = NULL;
     char *vports = NULL;
@@ -127,4 +127,12 @@ cleanup:
     return ret;
 }
 
+#else
+
+int
+detect_scsi_host_caps(union _virNodeDevCapData *d ATTRIBUTE_UNUSED)
+{
+    return -1;
+}
+
 #endif /* __linux__ */