LoongArch: Update help info of ARCH_STRICT_ALIGN

LoongArch: Update help info of ARCH_STRICT_ALIGN

Loongson-3A6000 and 3C6000 CPUs also support unaligned memory access, so
the current description is out of date to some extent.

Actually, all of Loongson-3 series processors based on LoongArch support
unaligned memory access, this hardware capability is indicated by the bit
20 (UAL) of CPUCFG1 register, update the help info to reflect the reality.

Cc: stable@vger.kernel.org
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>