target/arm: Fix big-endian handling of NEON gdb remote debugging

target/arm: Fix big-endian handling of NEON gdb remote debugging

In the code for allowing the gdbstub to set the value of an AArch64
FP/SIMD register, we weren't accounting for target_big_endian()
being true. This meant that for aarch64_be-linux-user we would
set the two halves of the FP register the wrong way around.
The much more common case of a little-endian guest is not affected;
nor are big-endian hosts.

Correct the handling of this case.

Cc: qemu-stable@nongnu.org
Signed-off-by: Vacha Bhavsar <vacha.bhavsar@oss.qualcomm.com>
Message-id: 20250722173736.2332529-2-vacha.bhavsar@oss.qualcomm.com
[PMM: added comment, expanded commit message, fixed missing space]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>