bpf, x86: Fix "no previous prototype" warning

stable inclusion
from stable-v5.10.85
commit f26951db84a4074a027aba1840370ceb928ba1a3
bugzilla: 186032 https://gitee.com/openeuler/kernel/issues/I4QVI4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f26951db84a4074a027aba1840370ceb928ba1a3



--------------------------------

commit f45b2974 upstream.

The arch_prepare_bpf_dispatcher function does not have a prototype, and
yields the following warning when W=1 is enabled for the kernel build.

  >> arch/x86/net/bpf_jit_comp.c:2188:5: warning: no previous \
  prototype for 'arch_prepare_bpf_dispatcher' [-Wmissing-prototypes]
        2188 | int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, \
	int num_funcs)
             |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~

Remove the warning by adding a function declaration to include/linux/bpf.h.

Fixes: 75ccbef6 ("bpf: Introduce BPF dispatcher")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Björn Töpel <bjorn@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211117125708.769168-1-bjorn@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>