Minor fixes

[richardeoin]

• [x] Add sdmmc-fatfs flag to docs.rs documentation render
• [x] Maximum Hyperbus memory size is 256MB
• [x] ~Update depreciated methods in chrono~

[richardeoin]

bors r+

[bors[bot]]

Build succeeded:

• ci (1.61.0, stm32h735)
• ci (1.61.0, stm32h743)
• ci (1.61.0, stm32h743v)
• ci (1.61.0, stm32h747cm7)
• ci (1.61.0, stm32h753)
• ci (1.61.0, stm32h753v)
• ci (1.61.0, stm32h7b0)
• ci (1.61.0, stm32h7b3)
• ci (stable, stm32h735)
• ci (stable, stm32h743)
• ci (stable, stm32h743v)
• ci (stable, stm32h747cm7)
• ci (stable, stm32h753)
• ci (stable, stm32h753v)
• ci (stable, stm32h7b0)
• ci (stable, stm32h7b3)
• Rustfmt