[SCSI] 53c700: update endian processing macros

This update now allows this driver to be used on big endian bus
machines that aren't parisc.  To do that, the driver must set a
CONFIG_53C700_BE_BUS in Kconfig to compile the right macro versions.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>