petti speed up for vdso

[thehajime]

https://lore.kernel.org/linux-um/m2o720w9b0.wl-thehajime@gmail.com/

int __vdso_clock_gettime(clockid_t clock, struct __kernel_old_timespec *ts)
{
	long ret;

#if 1
	asm("jmp *%4"
	    : "=a" (ret)
	    : "a" (__NR_clock_gettime), "D" (clock), "S" (ts), "r" (NR_syscalls + 0UL)
	    : "rcx", "r11", "memory");
#endif
	__VDSO_SYSCALL2(__NR_clock_gettime, ret, clock, ts);
	return ret;
}