testing: Fix syscall and RTC driver test issues

[fangpeina]

Summary

This PR fixes two test suite issues:

1. syscall test: Fix crash when CONFIG_FDCHECK is enabled
2. RTC driver test: Set default VENDOR_DELAY to 1 for reliable test execution

Impact

• Is new feature added? NO
• Is existing feature changed? YES - Fixed test compatibility issues
• Impact on user: YES - Tests now run reliably with CONFIG_FDCHECK and on various platforms
• Impact on build: NO
• Impact on hardware: NO
• Impact on documentation: NO
• Impact on security: NO
• Impact on compatibility: NO

Testing

Tested on the sim, qemu platform (e.g., qemu-armeabi-v7a) and real devices. Some sample test logs are listed below:

[   38.711910] [396] [  INFO] [ap] [==========] nuttx_syscall_test_suites: Running 1 test(s).
[   38.712465] [396] [  INFO] [ap] [ RUN      ] test_nuttx_syscall_dup02
[   38.654182] [396] [  INFO] [ap] [       OK ] test_nuttx_syscall_dup02
[   38.654578] [396] [  INFO] [ap] [  PASSED  ] 1 test(s).

[   31.497654] [268] [  INFO] [ap] [==========] nuttx_syscall_test_suites: Running 1 test(s).
[   31.498753] [268] [  INFO] [ap] [ RUN      ] test_nuttx_syscall_listen01
[   31.459617] [268] [  INFO] [ap] [       OK ] test_nuttx_syscall_listen01
[   31.460421] [268] [  INFO] [ap] [  PASSED  ] 1 test(s).

[22/03/25 10:21:58.887608] [147] [ap] [==========] tests: Running 3 test(s).
[22/03/25 10:21:58.888500] [147] [ap] [ RUN      ] test_case_rtc_01
[01/01/00 00:00:06.001100] [147] [ap] [       OK ] test_case_rtc_02
[01/01/00 00:00:11.001900] [ 3] [ap] rtc periodic callback trigger!!!
[01/01/00 00:00:26.004700] [147] [ap] [       OK ] test_case_rtc_03
[01/01/00 00:00:26.005500] [147] [ap] [  PASSED  ] 3 test(s).