Simplify i386, amd64 and x32 expedite registers

Simplify i386, amd64 and x32 expedite registers

Nowadays, there are a lot of duplication about
i386/{i386, amd64, x32}*-expedite in features/Makefile.  However,
in features/Makefile, we have

 echo "expedite:$(if $($*-expedite),$($*-expedite),$($(firstword $(subst -, ,$(notdir $*)))-expedite))" \
	  >> $(outdir)/$*.tmp

which means for a given bar/foo-baz.xml, we'll look for either
bar/foo-baz-expedite or foo-expedite.  In x86 expedite registers, we
use the former now, but it will be much simpler if we use the latter.
This is what this patch does.  This patch removes them, and defines
three generic expedite.  Re-run 'make GDB=/path/build/gdb all' to
regenerate regformats/*.dat files, and they are not changed.

gdb:

2016-10-05  Yao Qi  <yao.qi@linaro.org>

	* features/Makefile: Remove i386/*-expedite. Add i386-expedite,
	amd64-expedite, and x32-expedite.