Blackfin: delete fork func

We don't implement fork() since we are no-mmu, so redirect it to the
existing ENOSYS stub rather than adding a custom EINVAL one.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Bob Liu <lliubbo@gmail.com>
diff --git a/arch/blackfin/include/asm/unistd.h b/arch/blackfin/include/asm/unistd.h
index 75ec9df..3287222 100644
--- a/arch/blackfin/include/asm/unistd.h
+++ b/arch/blackfin/include/asm/unistd.h
@@ -11,7 +11,7 @@
  */
 #define __NR_restart_syscall	  0
 #define __NR_exit		  1
-#define __NR_fork		  2
+				/* 2 __NR_fork not supported on nommu */
 #define __NR_read		  3
 #define __NR_write		  4
 #define __NR_open		  5