libspl: move remaining ddi_* prototypes from zfs_context.h

Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes #17861

include/sys/zfs_context.h

@@ -77,8 +77,6 @@ extern "C" {
 #include <sys/zfs_context_os.h>
 #else /* _KERNEL || _STANDALONE */
 
-#define	_SYS_SUNDDI_H
-
 #include <stdio.h>
 #include <stdlib.h>
 #include <stddef.h>
@@ -210,12 +208,6 @@ typedef off_t loff_t;
 extern int highbit64(uint64_t i);
 extern int lowbit64(uint64_t i);
 
-/*
- * Hostname information
- */
-extern int ddi_strtoull(const char *str, char **nptr, int base,
-    u_longlong_t *result);
-
 /*
  * Kernel modules
  */