Linux: Fix 32-bit vDSO for clock_gettime on powerpc32

When the clock_id is CLOCK_PROCESS_CPUTIME_ID or CLOCK_THREAD_CPUTIME_ID,
on the 5.10 kernel powerpc 32-bit, the 32-bit vDSO is executed successfully (
because the __kernel_clock_gettime in arch/powerpc/kernel/vdso32/gettimeofday.S
does not support these two IDs, the 32-bit time_t syscall will be used),
but tp32.tv_sec is equal to 0, causing the 64-bit time_t syscall to continue to be used,
resulting in two system calls.

Fix commit 72e84d1d.

Signed-off-by: maminjie <maminjie2@huawei.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>