kernel/time/posix-stubs.c: remove duplicated include

kernel/time/posix-stubs.c: remove duplicated include

./kernel/time/posix-stubs.c: linux/syscalls.h is included more than once.

Link: https://lkml.kernel.org/r/20230608082312.123939-1-yang.lee@linux.alibaba.com
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=5463
Fixes: c1956519cd7e ("syscalls: add sys_ni_posix_timers prototype")
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>