Avoid mapping ENOENT to ENOTDIR for non-existent path components.

The ENOTDIR mapping was introduced in r235266 for kern/128933 based on
an interpretation of the somewhat ambiguous language in the POSIX realpath
specification.  The interpretation is inconsistent with Solaris and Linux,
a regression from 9.0, and does not appear to be permitted by the
description of ENOTDIR:

     20 ENOTDIR Not a directory.  A component of the specified pathname
             existed, but it was not a directory, when a directory was
             expected.

PR:		standards/171577
MFC after:	3 days

lib/libc/stdlib/realpath.c

@@ -181,8 +181,6 @@ realpath(const char * __restrict path, char * __restrict resolved)
 			return (NULL);
 		}
 		if (lstat(resolved, &sb) != 0) {
-			if (errno != ENOENT || p != NULL)
-				errno = ENOTDIR;
 			if (m)
 				free(resolved);
 			return (NULL);