staging: r8188eu: fix the index check in mgt_dispatcher

staging: r8188eu: fix the index check in mgt_dispatcher

In mgt_dispatcher, we check that index is a valid index for the
mlme_sta_tbl array. The valid indices for this array are from 0 to
ARRAY_SIZE(mlme_sta_tbl) - 1.

An invalid index is >= ARRAY_SIZE(mlme_sta_tbl). Fix the off by one error
in the check.

Fixes: db84803cd8de ("staging: r8188eu: use ARRAY_SIZE for mlme_sta_tbl")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220422140958.239767-1-martin@kaiser.cx
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>