MIPS: Go back with the default Linux # of registers to 90

MIPS: Go back with the default Linux # of registers to 90

Set the number of registers for non-XML-described Linux targets to 90,
reverting a change made here with the addition of DSP register support:

commit 1faeff088bbbd037d7769d214378b4faf805fa2e
Author: Maciej W. Rozycki <macro@linux-mips.org>
Date:   Thu Mar 1 22:19:48 2012 +0000

and fixing a regression introduced for legacy `gdbserver' targets
causing a "Remote 'g' packet reply is too long" error message where the
amount of register data received with a `g' packet (90) exceeds the
maximum number of registers expected (79).

Update the setting for XML-described targets, reflecting the actual
number of registers which have been assigned numbers, matching the:

      gdb_assert (gdbarch_num_regs (gdbarch) <= MIPS_RESTART_REGNUM);

requirement in `mips_linux_init_abi'.

	gdb/
	* mips-tdep.c (mips_gdbarch_init): For GDB_OSABI_LINUX set
	`num_regs' to 90 rather than 79.  Where a target description is
	present adjust the setting appropriately.