lib/mkhtemp.c: use standard suffix

it may seem counterintuitive that a shorter suffix is
better, but i think we should ideally look just like
what is made my any other tool, and other mktemp
tools generate:

tmp.XXXXXXXXXX

this is the default, but of course it could be changed.

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/libreboot-utils/lib/mkhtemp.c

@@ -50,8 +50,7 @@ new_tmp_common(int *fd, char **path, int type)
 #endif
 	struct stat st;
 
-	char suffix[] =
-	    "tmpXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX";
+	char suffix[] = "tmp.XXXXXXXXXX";
 	char *tmpdir = NULL;
 
 	int close_errno;
@@ -582,7 +581,7 @@ mkhtemp(int *fd,
 	while (end > template && *--end == 'X')
 		xc++;
 
-	if (xc < 12 || xc > len) {
+	if (xc < 6 || xc > len) {
 		errno = EINVAL;
 		return -1;
 	}