riscv: Remove unused TASK_TI_FLAGS

Since commit f0bddf50 ("riscv: entry: Convert to generic
entry"), TASK_TI_FLAGS is not used any more, so remove it.

Fixes: f0bddf50 ("riscv: entry: Convert to generic entry")
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/20241109014605.2801492-1-ruanjinjie@huawei.com


Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>