selftests/ftrace: Add new test case which adds multiple consecutive probes in a function

Commit 97f88a3d ("powerpc/kprobes: Fix null pointer reference in
arch_prepare_kprobe()") fixed a recent kernel oops that was caused as
ftrace-based kprobe does not generate kprobe::ainsn::insn and it gets
set to NULL.
Add new test case kprobe_insn_boundary.tc which adds a
kprobe at every byte within $FUNCTION_FORK up to an offset of 256 bytes,
to be able to test potential issues with kprobes on
successive instructions.
The '|| continue' is added with the echo statement to ignore errors that
are caused by trying to add kprobes to non probeable lines and continue
with the test.

Link: https://lore.kernel.org/linux-trace-kernel/20230428163842.95118-2-akanksha@linux.ibm.com



Signed-off-by: Akanksha J N <akanksha@linux.ibm.com>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>