ABI for aarch64: register x0-x7 are used for parameter and result. In
bcc, there are 6 parameter registers are defined. So use x0-x5 as
parameter. frame pointer, link register, stack pointer and pc are added
in PT_REGS_xx according to arm64 architecture.

syscall number of bpf for aarch64 are defined in Kernel
header uapi/asm-generic/unistd.h.
Signed-off-by: Zhiyi Sun <zhiyisun@gmail.com>