usb: mtu3: fix memory corruption in mtu3_debugfs_regset()

This code is using the wrong sizeof() so it does not allocate enough
memory.  It allocates 32 bytes but 72 are required.  That will lead to
memory corruption.

Fixes: ae078092 ("usb: mtu3: add debugfs interface files")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/X8ikqc4Mo2/0G72j@mwanda


Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>