clocksource/drivers/riscv: Fix clocksource mask

clocksource/drivers/riscv: Fix clocksource mask

For all riscv architectures (RV32, RV64 and RV128), the clocksource
is a 64 bit incrementing counter.

Fix the clock source mask accordingly.

Tested on both 64bit and 32 bit virt machine in QEMU.

Fixes: 62b019436814 ("clocksource: new RISC-V SBI timer driver")
Signed-off-by: Atish Patra <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Anup Patel <[email protected]>
Cc: Albert Ou <[email protected]>
Cc: Daniel Lezcano <[email protected]>
Cc: [email protected]
Cc: Palmer Dabbelt <[email protected]>
Cc: Anup Patel <[email protected]>
Cc: Damien Le Moal <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]