LoongArch: Silence the boot warning about 'nokaslr'

The kernel parameter 'nokaslr' is handled before start_kernel(), so we
don't need early_param() to mark it technically. But it can cause a boot
warning as follows:

Unknown kernel command line parameters "nokaslr", will be passed to user space.

When we use 'init=/bin/bash', 'nokaslr' which passed to user space will
even cause a kernel panic. So we use early_param() to mark 'nokaslr',
simply print a notice and silence the boot warning (also fix a potential
panic). This logic is similar to RISC-V.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>