wifi: ath12k: Fix buffer overflow in debugfs

wifi: ath12k: Fix buffer overflow in debugfs

If the user tries to write more than 32 bytes then it results in memory
corruption.  Fortunately, this is debugfs so it's limited to root users.

Fixes: 3f73c24f28b3 ("wifi: ath12k: Add support to enable debugfs_htt_stats")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Vasanthakumar Thiagarajan <vasanthakumar.thiagarajan@oss.qualcomm.com>
Link: https://patch.msgid.link/35daefbd-d493-41d9-b192-96177d521b40@stanley.mountain
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>