Fix: Variable initialization for TIMD of SGPM

Hyeongmun Jang requested to merge hm.jang/ECM:FIX_SGPM_UINT64 into master

for TIMD derivation process of SGPM,

Variable uiCostHor/uiCostVer which has uint64_t type is initialized to be -1. and the vaule of these variables are accumulated with template cost after that.

Hence, if template cost is exactly 0, the cost is still set to be MAX-1. it seems unusual.

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