Move zfs_config.h include to command line -include

Remove the few places in the code where zfs_config.h is included.
It is now added to the gcc compile line to ensure the config results
are always available.

module/avl/avl.c

@@ -1033,7 +1033,6 @@ done:
 }
 
 #if defined(_KERNEL) && defined(HAVE_SPL)
-#include "zfs_config.h"
 
 static int avl_init(void) { return 0; }
 static int avl_fini(void) { return 0; }

module/nvpair/nvpair.c

@@ -3246,7 +3246,6 @@ nvs_xdr(nvstream_t *nvs, nvlist_t *nvl, char *buf, size_t *buflen)
 }
 
 #if defined(_KERNEL) && defined(HAVE_SPL)
-#include "zfs_config.h"
 
 static int nvpair_init(void) { return 0; }
 static int nvpair_fini(void) { return 0; }

module/unicode/u8_textprep.c

@@ -2133,7 +2133,6 @@ u8_textprep_str(char *inarray, size_t *inlen, char *outarray, size_t *outlen,
 }
 
 #if defined(_KERNEL) && defined(HAVE_SPL)
-#include "zfs_config.h"
 
 static int unicode_init(void) { return 0; }
 static int unicode_fini(void) { return 0; }

module/zcommon/zfs_prop.c

@@ -534,7 +534,6 @@ zfs_prop_align_right(zfs_prop_t prop)
 #endif
 
 #if defined(_KERNEL) && defined(HAVE_SPL)
-#include "zfs_config.h"
 
 static int zcommon_init(void) { return 0; }
 static int zcommon_fini(void) { return 0; }