x86/dumpstack: Don't mention RIP in "Code: "

Commit

  238c9111 ("x86/dumpstack: Fix misleading instruction pointer error message")

changed the "Code:" line in bug reports when RIP is an invalid pointer.
In particular, the report currently says (for example):

  BUG: kernel NULL pointer dereference, address: 0000000000000000
  ...
  RIP: 0010:0x0
  Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.

That

  Unable to access opcode bytes at RIP 0xffffffffffffffd6.

is quite confusing as RIP value is 0, not -42. That -42 comes from
"regs->ip - PROLOGUE_SIZE", because Code is dumped with some prologue
(and epilogue).

So do not mention "RIP" on this line in this context.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/b772c39f-c5ae-8f17-fe6e-6a2bc4d1f83b@kernel.org