standalone eepro100_eeprom: fix build error

Building examples/standalone/eepro100_eeprom triggers this error:

In file included from include/common.h:629,
                 from eepro100_eeprom.c:24:
include/net.h: In function 'NetReadIP':
include/net.h:430: warning: implicit declaration of function 'memcpy'
eepro100_eeprom.c: At top level:
eepro100_eeprom.c:81: error: conflicting types for 'memcpy'
include/net.h:430: error: previous implicit declaration of 'memcpy' was here

Fix this.

Signed-off-by: Wolfgang Denk <wd@denx.de>