compat: Fix sparse address space warnings

In compat_sys_old_getrlimit() we pass a kernel pointer to
sys_old_getrlimit() inside a set_fs() bracket.  This is okay, so we
can safely cast the affected pointer to __user.

In compat_clock_nanosleep_restart(), the variable "rmtp" holds a user
pointer.  Annotate it as such.

Both of these warnings are ancient, but were reported by Fengguang
Wu's test system due to other changes.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Toyo Abe <toyoa@mvista.com>
Link: http://lkml.kernel.org/n/tip-507h7cq5e45eg6ygtykon3bf@git.kernel.org