target/alpha: Honor the FEN bit

This bit is used by NetBSD for lazy fpu migration.

Tested-by: Jason Thorpe <thorpej@me.com>
Reported-by: Jason Thorpe <thorpej@me.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/438
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
1 file changed