Samsung provides many firmware upgrade in the format of a .dat
file, at least for nearly all YP's (checked for Q2, R0, T10, Z5).
This is a simple cyclic xor which a fixed key, a md5 sum and a
header specifying the model/version/region.
Change-Id: Ib0461a74196383189fd2d8162da444a85a229c60
