target/mips: Require even maskbits in update_pagemask

target/mips: Require even maskbits in update_pagemask

The number of bits set in PageMask must be even.

Fixes: d40b55bc1b86 ("target/mips: Fix PageMask with variable page size")
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250328175526.368121-3-richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Cc: qemu-stable@nongnu.org
(cherry picked from commit d89b9899babcc01d7ee75f2917da861dc2afbc27)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>