Merge branch 'bpf_trace_printk-percent-s'

Alexei Starovoitov says:

====================
support for '%s' in bpf_trace_printk

v2->v3:
fix the comment to mention that strncpy_from_unsafe() returns
the length of the string including the trailing NUL.

v1->v2:
patch 1: generalize FETCH_FUNC_NAME(memory, string) into
strncpy_from_unsafe()
patch 2: use it in bpf_trace_printk
====================

Signed-off-by: David S. Miller <davem@davemloft.net>