altosui: Remove extra AltosEepromBlock layer

This was interposed between the download layer and the eeprom layer to
hold a eeprom block full of flight log records. The addition of the tiny
log format required reworking the code to hold chunks full of eeprom
data without regard to their content, so this content-specific layer
didn't seem useful anymore.

Signed-off-by: Keith Packard <keithp@keithp.com>