fix: enable ppoll libc API

1.modifications:
deleted:    porting/liteos_a/user/src/linux/ppoll.c
2.influence:
none
Signed-off-by: Nteamol <28105285@qq.com>

porting/liteos_a/user/src/linux/ppoll.c

-#define _GNU_SOURCE
-#include <poll.h>
-#include <signal.h>
-#include <errno.h>
-#include "syscall.h"
-#include <unsupported_api.h>
-
-#define IS32BIT(x) !((x)+0x80000000ULL>>32)
-#define CLAMP(x) (int)(IS32BIT(x) ? (x) : 0x7fffffffU+((0ULL+(x))>>63))
-
-int ppoll(struct pollfd *fds, nfds_t n, const struct timespec *to, const sigset_t *mask)
-{
-	time_t s = to ? to->tv_sec : 0;
-	long ns = to ? to->tv_nsec : 0;
-	unsupported_api(__FUNCTION__);
-#ifdef SYS_ppoll_time64
-	int r = -ENOSYS;
-	if (SYS_ppoll == SYS_ppoll_time64 || !IS32BIT(s))
-		r = __syscall_cp(SYS_ppoll_time64, fds, n,
-			to ? ((long long[]){s, ns}) : 0,
-			mask, _NSIG/8);
-	if (SYS_ppoll == SYS_ppoll_time64 || r != -ENOSYS)
-		return __syscall_ret(r);
-	s = CLAMP(s);
-#endif
-	return syscall_cp(SYS_ppoll, fds, n,
-		to ? ((long[]){s, ns}) : 0, mask, _NSIG/8);
-}