lib: utils/timer: mtimer: add separate T-Head C9xx CLINT mtimer compatible

T-HEAD allows soc vendor to map the mtimer and mswi of C9xx clint on
different address, which may cause a misuse if use the same compatible
string, add a new timer compatible string to avoid this.

Signed-off-by: Inochi Amaoto <inochiama@outlook.com>
Link: https://lore.kernel.org/linux-riscv/6e48cbe5e60f9ada2fd1fe58e803e127f1a678e5.1696433229.git.unicorn_wang@outlook.com/


Reviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Anup Patel <anup@brainfault.org>