Remove support for "target m32rsdi" and "target mips/pmon/ddb/rockhopper/lsi"

Remove support for "target m32rsdi" and "target mips/pmon/ddb/rockhopper/lsi"

This removes support for:

 | target            | source                |
 |-------------------+-----------------------|
 | target m32rsdi    | gdb/remote-m32r-sdi.c |
 | target mips       | gdb/remote-mips.c     |
 | target pmon       | gdb/remote-mips.c     |
 | target ddb        | gdb/remote-mips.c     |
 | target rockhopper | gdb/remote-mips.c     |
 | target lsi        | gdb/remote-mips.c     |

That is:

 - Remote M32R debugging over SDI.

 - Debugging boards using the MIPS remote debugging protocol
   over a serial line, PMON, and a few variants.

These are the last non-"target remote" remote targets in the tree, if
you don't count "target sim".

Refs:

 https://sourceware.org/ml/gdb/2016-03/msg00004.html
 https://sourceware.org/ml/gdb-patches/2016-03/msg00580.html

gdb/ChangeLog:
2016-03-31  Pedro Alves  <palves@redhat.com>

	* NEWS: Mention that support for "target m32rsdi", "target mips",
	"target pmon", "target ddb", "target rockhopper", and "target lsi"
	was removed.
	* Makefile.in (ALL_TARGET_OBS): Remove remote-m32r-sdi.o and
	remote-mips.o.
	(ALLDEPFILES): Remove remote-m32r-sdi.c and remote-mips.c.
	* configure.tgt: Remove all references to remote-m32r-sdi.o and
	remote-mips.o.
	* mips-tdep.c (deprecated_mips_set_processor_regs_hack): Delete
	function.
	* mips-tdep.h (deprecated_mips_set_processor_regs_hack): Delete
	declaration.
	* remote-m32r-sdi.c, remote-mips.c: Delete files.
	* symfile.c (generic_load, generic_load): Remove comments.

gdb/doc/ChangeLog:
2016-03-31  Pedro Alves  <palves@redhat.com>

	* gdb.texinfo (M32R/SDI): Delete node.
	(MIPS Embedded): Remove references to the MIPS remote debugging
	protocol, PMON and variants, and the associated commands.