objtool: Add stackleak instrumentation to uaccess safe list

If a function has a large stack frame, the stackleak plugin adds a call
to stackleak_track_stack() after the prologue.

This function may be called in uaccess-enabled code.  Add it to the
uaccess safe list.

Fixes the following warning:

  vmlinux.o: warning: objtool: kasan_report+0x12: call to stackleak_track_stack() with UACCESS enabled

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/42e9b487ef89e9b237fd5220ad1c7cf1a2ad7eb8.1681320562.git.jpoimboe@kernel.org