misc: i2c_eeprom: consider pagesize when writing to eeprom

Calculate the maximum length of the buffer when writing
across the page boundary. If the buffer length (len)
exceeds the page boundary (pagesize), split it. Use this
length instead of comparing the length with the pagesize,
because if the write start address (offset) is not at the
beginning of a page and the page_offset + len is greater
than the page boundary (pagesize), the write operation
would overflow the current page and the behaviour can be
undefined (e.g. at24).

Signed-off-by: Alex Michel <alex.michel@wiedemann-group.com>