chore: fix C lint errors

[Shivam-1827]

Resolves #6105

Description

What is the purpose of this pull request?

This pull request:

• Fixes a coding style issue where the variable x1 was not declared as a pointer to const in t_u.c.
• Updates all occurrences where x1 can be declared as const, improving code safety and reducing unintended modifications.

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves Fix C lint errors #6105

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

• The changes were applied to the following lines in t_u.c:
  • 209, 296, 383, 470, 557, 644, 731, 818, 905, 992, 1079, 1166, 1253, 1340, 1427, 1514, 1601, 1688, 1775, 1862
• Ensured the changes follow the required coding style guidelines.

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• Read, understood, and followed the contributing guidelines.

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[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
ndarray/base/assign	$\color{red}4632/10439$ $\color{green}+44.37\%$	$\color{green}44/44$ $\color{green}+100.00\%$	$\color{red}0/43$ $\color{green}+0.00\%$	$\color{red}4632/10439$ $\color{green}+44.37\%$

The above coverage report was generated for the changes in this PR.