RISC-V: User-Visible Changes

This merge contains the user-visible, ABI-breaking changes that we want
to make sure we have in Linux before our first release.   Highlights
include:

* VDSO entries for clock_get/gettimeofday/getcpu have been added.  These
  are simple syscalls now, but we want to let glibc use them from the
  start so we can make them faster later.
* A VDSO entry for instruction cache flushing has been added so
  userspace can flush the instruction cache.
* The VDSO symbol versions for __vdso_cmpxchg{32,64} have been removed,
  as those VDSO entries don't actually exist.

Conflicts:
        arch/riscv/include/asm/tlbflush.h

arch/riscv/include/asm/tlbflush.h

@@ -17,6 +17,8 @@
 
 #ifdef CONFIG_MMU
 
+#include <linux/mm_types.h>
+
 /*
  * Flush entire local TLB.  'sfence.vma' implicitly fences with the instruction
  * cache as well, so a 'fence.i' is not necessary.