microblaze: Microblaze wants sys_fork for noMMU too

The patch "generic sys_fork / sys_vfork / sys_clone"
(sha1: d212504)
introduced generic sys_fork with implementation for noMMU
which returns EINVAL for noMMU.

and the patch "microblaze: switch to generic fork/vfork/clone"
(sha1: f3268ed)
enable sys_fork only for MMU which is causing compilation
failure on noMMU system.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/include/asm/unistd.h

@@ -37,9 +37,7 @@
 #define __ARCH_WANT_SYS_RT_SIGSUSPEND
 #define __ARCH_WANT_SYS_CLONE
 #define __ARCH_WANT_SYS_VFORK
-#ifdef CONFIG_MMU
 #define __ARCH_WANT_SYS_FORK
-#endif
 
 /*
  * "Conditional" syscalls