This patch implements the reading functionality for the generic I2C
EEPROM driver, which was just a non-functional stub until now.

Since the page size will be of importance for the writing support, we
add suitable members to the private data structure to keep track of it.

Compatibility strings for a range of at24c* chips are added.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heiko Schocher <hs@denx.de>

drivers/misc/i2c_eeprom.c fails to build unless CONFIG_FIT_SIGNATURE
is defined.

  CC      drivers/misc/i2c_eeprom.o
drivers/misc/i2c_eeprom.c: In function 'i2c_eeprom_read':
drivers/misc/i2c_eeprom.c:15:10: error: 'ENODEV' undeclared
(first use in this function)
drivers/misc/i2c_eeprom.c:15:10: note: each undeclared identifier
is reported only once for each function it appears in
drivers/misc/i2c_eeprom.c: In function 'i2c_eeprom_write':
drivers/misc/i2c_eeprom.c:21:10: error: 'ENODEV' undeclared
(first use in this function)
drivers/misc/i2c_eeprom.c:22:1: warning: control reaches end of
non-void function [-Wreturn-type]
drivers/misc/i2c_eeprom.c: In function 'i2c_eeprom_read':
drivers/misc/i2c_eeprom.c:16:1: warning: control reaches end of
non-void function [-Wreturn-type]
make[2]: *** [drivers/misc/i2c_eeprom.o] Error 1
make[1]: *** [drivers/misc] Error 2
make: *** [drivers] Error 2

By the way, Sandbox (enabling CONFIG_FIT_SIGNATURE) is luckily
working depending on it.
Sandbox includes include/asm-generic/errno.h
            from include/errno.h
            from include/u-boot/rsa-checksum.h
            from include/image.h
            from include/common.h
            from drivers/misc/i2c_eeprom.c

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Simon Glass <sjg@chromium.org>

There seem to be a few EEPROM drivers around - perhaps we should have a
single standard one? This simple driver is used for sandbox testing, but
could be pressed into more active service.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Heiko Schocher <hs@denx.de>
Reviewed-by: Masahiro Yamada <yamada.m@jp.panasonic.com>