tune-microblaze-features.inc: Force either 'el' or 'eb' for TUNE_ARCH
tune-microblaze-features.inc: Force either 'el' or 'eb' for TUNE_ARCH

* Change the TUNE_ARCH variable so that for MicroBlaze the endianess in
  part of the TUNE_ARCH value
* This causes the triplet for MicroBlaze targets to have either
  microblazeel or microblazeeb and prevents any confusion about defaults

Signed-off-by: Nathan Rossi <e1e6d173c6873c0ae2b831215d22380d293bb314@xilinx.com>

Xilinx/meta-xilinx,Xilinx/meta-xilinx,Xilinx/meta-xilinx,Xilinx/meta-xilinx,nathanrossi/meta-xilinx,Xilinx/meta-xilinx,nathanrossi/meta-xilinx,Xilinx/meta-xilinx,nathanrossi/meta-xilinx,nathanrossi/meta-xilinx