fix: add syscall for ppoll & add 2 testcases

1.modifications:
modified:   syscall/los_syscall.h
modified:   syscall/misc_syscall.c
modified:   syscall/syscall_lookup.h
2.add 3 testcases:
testsuites/unittest/IO/full/IO_test_ppoll_001.cpp
testsuites/unittest/IO/full/IO_test_ppoll_002.cpp
3.influence:
none

Signed-off-by: teamol <28105285@qq.com>

testsuites/unittest/IO/BUILD.gn

@@ -83,6 +83,8 @@ sources_full = [
   "full/IO_test_gettext_001.cpp",
   "full/IO_test_strncasecmp_l_001.cpp",
   "full/IO_test_strncasecmp_l_002.cpp",
+  "full/IO_test_ppoll_001.cpp",
+  "full/IO_test_ppoll_002.cpp",
 ]
 
 if (LOSCFG_USER_TEST_LEVEL >= TEST_LEVEL_LOW) {