Fix overrun in st7565_write_raw when not at (0, 0)

[bcat]

Description

Takes the OLED fix from #13204 in master and applies it to ST7565 in develop, as requested in a comment on that PR.

I don't have the requisite hardware to test this, but at least I don't see any new build errors introduced in the make all:default.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout/userspace (addition or update)
• Documentation

Issues Fixed or Closed by This PR

• Related to [Bug] oled_write_raw overruns data buffer, corrupts display when cursor not at origin (0, 0) #13203.

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).