target/arm: Fix SME ST1Q

target/arm: Fix SME ST1Q

A typo, noted in the bug report, resulting in an
incorrect write offset.

Cc: qemu-stable@nongnu.org
Fixes: 7390e0e9ab8 ("target/arm: Implement SME LD1, ST1")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1833
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20230818214255.146905-1-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
(cherry picked from commit 4b3520fd93cd49cc56dfcab45d90735cc2e35af7)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>