LoongArch/irq: Use seq_put_decimal_ull_width() for decimal values

Performance improvement for reading /proc/interrupts on LoongArch.

On a system with n CPUs and m interrupts, there will be n*m decimal
values yielded via seq_printf(.."%10u "..) which is less efficient than
seq_put_decimal_ull_width(), stress reading /proc/interrupts indicates
~30% performance improvement with this patch (and its friends).

Signed-off-by: David Wang <00107082@163.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>