LoongArch: Complete KSave registers definition

According to the "LoongArch Reference Manual Volume 1: Basic
Architecture", the KSave registers (SAVE0-SAVE15) are defined in
Section 7.4.16 "Data Save (SAVE)" and listed in Table 7-1 "Control
and Status Registers Overview". These registers occupy the CSR
addresses from 0x30 to 0x3F, with 16 registers in total.

This patch completes the definitions of KS9 to KS15, so as to match
the architecture specification.

Reviewed-by: Wentao Guan <guanwentao@uniontech.com>
Signed-off-by: Yanteng Si <siyanteng@cqsoftware.com.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>