riscv: Update MIPS vendor id to 0x127

riscv: Update MIPS vendor id to 0x127

[1] defines MIPS vendor id as 0x127. All previous MIPS RISC-V patches
were tested on QEMU, also modified to use 0x722 as MIPS_VENDOR_ID. This
new value should reflect real hardware.

[1] https://mips.com/wp-content/uploads/2025/06/P8700_Programmers_Reference_Manual_Rev1.84_5-31-2025.pdf

Fixes: a8fed1bc03ac ("riscv: Add xmipsexectl as a vendor extension")
Signed-off-by: Chao-ying Fu <cfu@wavecomp.com>
Signed-off-by: Aleksa Paunovic <aleksa.paunovic@htecgroup.com>
Link: https://patch.msgid.link/20251113-mips-vendorid-v2-1-3279489b7f84@htecgroup.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Paul WAlmsley <pjw@kernel.org>