p54: fix EEPROM structure endianness

Since the EEPROM structure is read from hardware, it is
always little endian, annotate that in the struct and
make sure to convert where applicable.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Michael Wu <flamingice@sourmilk.net>
Tested-by: Florian Fainelli <florian.fainelli@telecomint.eu>
Signed-off-by: John W. Linville <linville@tuxdriver.com>