MIPS: Respect the "set mips compression" command

MIPS: Respect the "set mips compression" command

This fixes gdbarch matching, making sure one for the opposite compressed
ISA variation is not chosen.  That in turn makes "set mips compression"
work; right now the setting sticks to the initial value, either inferred
from the ELF header of the binary first loaded or the default value if
no binary has been used.  This only affects debugging with no symbol
table available or no binary chosen at all, as otherwise symbol
annotations determine the compressed ISA variation.

	* mips-tdep.c (mips_gdbarch_init): Also check the compressed ISA
	variation in gdbarch matching.