ext4/048: add check for od endian flag

ext4/048: add check for od endian flag

od --endian=little is used to read bytes in little endian when on a
big endian machine. Update test ext4/048 to require od endian flag
support on big endian machines, otherwise, skip test.

Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com>
Reviewed-by: Yang Xu <xuyang2018.jy@fujitsu.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>