power: olpc_battery: clean up eeprom read function

The change removes redundant sysfs binary file boundary check while
reading eeprom content from userspace, the check is done on caller
side in fs/sysfs/file.c, if binary attribute size is not zero.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>