libbb: add skip_dev_pfx()

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

libbb/skip_whitespace.c

@@ -30,3 +30,10 @@ char* FAST_FUNC skip_non_whitespace(const char *s)
 
 	return (char *) s;
 }
+
+char* FAST_FUNC skip_dev_pfx(const char *tty_name)
+{
+	if (strncmp(tty_name, "/dev/", 5) == 0)
+		tty_name += 5;
+	return (char*)tty_name;
+}