board/fsl/common: Fix eeprom system version endianness

SYSTEM ID EPPROM always store SYSTEM version info in big endian format.
SoC with ARM or PowerPC core should read/write version info from eeprom
in BIG endian format.

So use cpu-specific APIs to read SYSTEM version.

Signed-off-by: Jaiprakash Singh <b44839 at freescale.com>
Signed-off-by: Prabhakar Kushwaha <prabhakar at freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>