syzbot reported a potential read out of bounds in asus_report_fixup.

this patch adds checks so that a read out of bounds will not occur
Signed-off-by: Andrew Ballance <andrewjballance@gmail.com>
Reported-by:   <syzbot+07762f019fd03d01f04c@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=07762f019fd03d01f04c
Fixes: 59d2f5b7 ("HID: asus: fix more n-key report descriptors if n-key quirked")
Link: https://lore.kernel.org/r/20240602085023.1720492-1-andrewjballance@gmail.comSigned-off-by: Benjamin Tissoires <bentiss@kernel.org>