i2c_eeprom: include <linux/err.h> to fix build error

i2c_eeprom: include <linux/err.h> to fix build error

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>