target/mips: Don't check COP1X for 64 bit FP mode

target/mips: Don't check COP1X for 64 bit FP mode

Some implementations (i.e. Loongson-2F) may decide to implement
a 64 bit FPU without implementing COP1X instructions.

As the eligibility of 64 bit FP instructions is already determined
by CP0St_FR, there is no need to check for COP1X again.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20221102165719.190378-1-jiaxun.yang@flygoat.com>
[PMD: Add missing trailing parenthesis (buildfix)]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>