Optimize flash_make_cmd in drivers/cfi_flash.c for little endian

Fix "WARNING: flash_make_cmd: unsuppported LittleEndian mode"
message when probing for nonexistent flash in little endian mode.
As a side effect more efficient and smaller code is generated,
which is always a Good Thing (TM).
Patch by Ladislav Michl, 24 Sep 2005