mips: add a tune for using MIPS16e ASE instructions
The MIPS16e instruction set still has to be enabled by setting
MIPS_INSTRUCTION_SET = 'mips16e'
in e.g. distro.conf and can be disabled on a per-recipe basis as
needed.
This is a similar approach as is available on ARM for Thumb support.
Note that contrary to the ARM Thumb support in OE, we do add a new
OVERRIDE (mips16e), as there are some recipes in OE that need to be
compiled slightly differently if mips16e mode is requested.
Signed-off-by: André Draszik <adraszik@tycoint.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
