Fix wrong location for G109

[yunwei37]

Fix #742 : G109 tells the location at strconv.Atoi instead of strconv.Atoi result conversion to int16/32.

Before this commit, G109 will report on strconv.Atoi.
After this, it will report on the convertion likeint32(a).

[codecov-commenter]

Codecov Report

Merging #829 (3365f4a) into master (b0f3e78) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #829   +/-   ##
=======================================
  Coverage   74.35%   74.35%           
=======================================
  Files          50       50           
  Lines        3124     3124           
=======================================
  Hits         2323     2323           
  Misses        735      735           
  Partials       66       66           

Impacted Files	Coverage Δ
rules/integer_overflow.go	93.33% <100.00%> (ø)

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