1. RT_FIELD_PREP: prepare a bitfield element.
2. RT_FIELD_GET: extract a bitfield element.
3. rt_offsetof: member offset of a struct
4. rt_upper_32_bits: high 32 bits of value.
5. rt_lower_32_bits: lower 32 bits of value.
6. rt_upper_16_bits: high 16 bits of value.
7. rt_lower_16_bits: lower 16 bits of value.
8. rt_max_t: fix type of max(...).
9. rt_ilog2: integer logarithm base 2.
Signed-off-by: GuEe-GUI <2991707448@qq.com>