Retire spl_module_init()/spl_module_fini()

In the original implementation of the SPL wrappers were provided
for module initialization and cleanup.  This was done to abstract
away any compatibility code which might be needed for the SPL.

As it turned out the only significant compatibility issue was that
the default pwd during module load differed under Illumos and Linux.
Since this is such as minor thing and the wrappers complicate the
code they are being retired.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #2985

module/zfs/zfs_ioctl.c

@@ -186,7 +186,6 @@
 #include <sys/zfeature.h>
 
 #include <linux/miscdevice.h>
-#include <linux/module_compat.h>
 
 #include "zfs_namecheck.h"
 #include "zfs_prop.h"
@@ -5954,11 +5953,18 @@ zfs_allow_log_destroy(void *arg)
 #define	ZFS_DEBUG_STR	""
 #endif
 
-int
+static int __init
 _init(void)
 {
 	int error;
 
+	error = vn_set_pwd("/");
+	if (error) {
+		printk(KERN_NOTICE
+		    "ZFS: Warning unable to set pwd to '/': %d\n", error);
+		return (error);
+	}
+
 	spa_init(FREAD | FWRITE);
 	zfs_init();
 
@@ -5996,7 +6002,7 @@ out1:
 	return (error);
 }
 
-int
+static void __exit
 _fini(void)
 {
 	zfs_detach();
@@ -6010,13 +6016,11 @@ _fini(void)
 
 	printk(KERN_NOTICE "ZFS: Unloaded module v%s-%s%s\n",
 	    ZFS_META_VERSION, ZFS_META_RELEASE, ZFS_DEBUG_STR);
-
-	return (0);
 }
 
 #ifdef HAVE_SPL
-spl_module_init(_init);
-spl_module_exit(_fini);
+module_init(_init);
+module_exit(_fini);
 
 MODULE_DESCRIPTION("ZFS");
 MODULE_AUTHOR(ZFS_META_AUTHOR);