proc/kcore: Remove unused kclist_add_remap()

Commit

  bf904d27

 ("x86/pti/64: Remove the SYSCALL64 entry trampoline")

removed the sole usage of kclist_add_remap() but it did not remove the
left-over definition from the include file.

Fix the same.

Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Anderson <anderson@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Kairui Song <kasong@redhat.com>
Cc: kexec@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Omar Sandoval <osandov@fb.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/1553583028-17804-1-git-send-email-bhsharma@redhat.com