fsl: Fix compiler warnings from gcc-4.4 in sys_eeprom code

sys_eeprom.c: In function 'do_mac':
sys_eeprom.c:323: warning: dereferencing type-punned pointer will break strict-aliasing rules
sys_eeprom.c: In function 'mac_read_from_eeprom':
sys_eeprom.c:395: warning: dereferencing type-punned pointer will break strict-aliasing rules

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>