kselftest/arm64: Fix printf() compiler warnings in the arm64 syscall-abi.c tests

Fix the incorrect length modifiers in arm64/abi/syscall-abi.c.

Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Mark Brown <broonie@kernel.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241108134920.1233992-4-catalin.marinas@arm.com


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>