Fix conversion from GDB register profile to rizin profile

[ret2libc]

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 documented or updated the documentation of every function and struct this PR changes. If not so I've explained why.
• I've added tests that prove my fix is effective or that my feature works (if possible)
• I've updated the rizin book with the relevant information (if needed)

Detailed description

scanf("%s") uses are not safe, limit the number of characters read.

Test plan

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Closing issues

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[XVilka]

Translation unit diagnostic at <rizin/librz/debug/p/debug_gdb.c:221:4>: 'sscanf' may overflow; destination buffer in argument 3 has size 99, but the corresponding specifier may require size 101