staging: rtl8192u: propagate errors in rtl8192_read_eeprom_info

Propagate error from eprom_read and change the return type of
rtl8192_read_eeprom_info from void to int.

Signed-off-by: Salah Triki <salah.triki@acm.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>