bpf: pull in pkt_sched.h header for tooling to fix bpftool build

Dan reported that bpftool does not compile for him:

  $ make tools/bpf
    DESCEND  bpf

  Auto-detecting system features:
  ..                        libbfd: [ on  ]
  ..        disassembler-four-args: [ OFF ]

    DESCEND  bpftool

  Auto-detecting system features:
  ..                        libbfd: [ on  ]
  ..        disassembler-four-args: [ OFF ]

    CC       /opt/linux.git/tools/bpf/bpftool/net.o
  In file included from /opt/linux.git/tools/include/uapi/linux/pkt_cls.h:6:0,
                 from /opt/linux.git/tools/include/uapi/linux/tc_act/tc_bpf.h:14,
                 from net.c:13:
  net.c: In function 'show_dev_tc_bpf':
  net.c:164:21: error: 'TC_H_CLSACT' undeclared (first use in this function)
    handle = TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_INGRESS);
  [...]

Fix it by importing pkt_sched.h header copy into tooling
infrastructure.

Fixes: 49a249c3 ("tools/bpftool: copy a few net uapi headers to tools directory")
Fixes: f6f3...