analysis_arm_cs.c: Fix -Wmaybe-uninitialized warning in optimized capstone-v3 build

[kazarmy]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository
• I made sure to follow the project's coding style
• I've added tests that prove my fix is effective or that my feature works (if possible)
• I've updated the documentation and the rizin book with the relevant information (if needed)

Detailed description

This pr fixes the following warning in the capstone-v3 build of #260 (https://github.com/rizinorg/rizin/runs/2065028270#step:12:1323):

This is basically a mechanical blindfix which practically initializes i to 1, but since we don't run tests on capstone-v3 I'm not sure whether it's worth going deeper on this.

Test plan

All builds are green.

Closing issues

...

[codecov]

Codecov Report

Merging #800 (1d3b29b) into dev (2d3ecfc) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev     #800      +/-   ##
==========================================
- Coverage   42.80%   42.79%   -0.01%     
==========================================
  Files         871      871              
  Lines      316847   316850       +3     
==========================================
- Hits       135626   135609      -17     
- Misses     181221   181241      +20     

Impacted Files	Coverage Δ
librz/analysis/p/analysis_arm_cs.c	75.68% <ø> (ø)
librz/socket/rzpipe.c	44.32% <0.00%> (-10.57%)	⬇️
librz/util/intervaltree.c	94.51% <0.00%> (+0.03%)	⬆️
librz/util/pj.c	86.22% <0.00%> (+0.07%)	⬆️

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