fix(hid): Fix scroll value truncation

[adolto]

Fix 8 bit truncation of 16 bit scroll values when passed into functions zmk_hid_mouse_scroll_set and zmk_hid_mouse_scroll_update.

Fixes: #2864

PR check-list

• Branch has a clean commit history
• Additional tests are included, if changing behaviors/core code that is testable.
• Proper Copyright + License headers added to applicable files (Generally, we stick to "The ZMK Contributors" for copyrights to help avoid churn when files get edited)
• Pre-commit used to check formatting of files, commit messages, etc.
• Includes any necessary documentation changes.

[caksoylar]

Looks right to me, although the int8_t vs. int16_t difference between move/scroll is pretty glaring in the header. @petejohanson was there an intention or is it just a bug that scroll uses 8 bit values?