Clean up x86 non-linux GDBserver target descriptions

Clean up x86 non-linux GDBserver target descriptions

In GDBserver, only tdesc_i386 and tdesc_amd64 are used.  There is no point
of generating these *.dat files (which are used to generate *.c files during
GDBserver build.).

gdb:

2017-08-09  Yao Qi  <yao.qi@linaro.org>

	* features/Makefile (WHICH): Remove i386/ non-linux stuff.
	* regformats/i386/amd64-avx-avx512.dat: Remove.
	* regformats/i386/amd64-avx-mpx-avx512-pku.dat: Remove.
	* regformats/i386/amd64-avx-mpx.dat:Remove.
	* regformats/i386/amd64-avx.dat: Remove.
	* regformats/i386/amd64-mpx.dat: Remove.
	* regformats/i386/i386-avx-avx512.dat: Remove.
	* regformats/i386/i386-avx-mpx-avx512-pku.dat: Remove.
	* regformats/i386/i386-avx-mpx.dat: Remove.
	* regformats/i386/i386-mmx.dat: Remove.
	* regformats/i386/i386-mpx.dat: Remove.

gdb/gdbserver:

2017-08-09  Yao Qi  <yao.qi@linaro.org>

	* configure.srv (srv_i386_regobj): Remove i386-avx.o,
	i386-avx-avx512.o, i386-avx-mpx-avx512-pku.o, i386-mpx.o,
	i386-avx-mpx.o and i386-mmx.o.
	(srv_amd64_regobj): Remove amd64-avx.o, amd64-avx-avx512.o,
	amd64-avx-mpx-avx512-pku.o, amd64-mpx.o and amd64-avx-mpx.o.
	(srv_i386_xmlfiles): Remove i386/i386-avx.xml,
	i386/i386-avx-avx512.xml, i386/i386-avx-mpx-avx512-pku.xml,
	i386/i386-mpx.xml, i386/i386-avx-mpx.xml and i386/i386-mmx.xml.
	(srv_amd64_xmlfile):i386/amd64-avx.xml, i386/amd64-avx-avx512.xml,
	i386/amd64-avx-mpx-avx512-pku.xml, i386/amd64-mpx.xml,
	i386/amd64-avx-mpx.xml.