ARC: bpf: define uapi for BPF_PROG_TYPE_PERF_EVENT program type

Define appropriate uapi for the BPF_PROG_TYPE_PERF_EVENT program type
by exporting the user_regs_struct structure instead of the pt_regs
structure that is in-kernel only.

Signed-off-by: Sergey Matyukevich <sergey.matyukevich@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@kernel.org>