Raise SIGFPE for ieee exceptions.

The other types, such as FSR_FTT_UNIMPFPOP, should not appear,
because we enable normal emulation of missing insns at the
start of sparc_cpu_realizefn().

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230216054516.1267305-15-richard.henderson@linaro.org>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>