target/i386: Use correct type for get_float_exception_flags() values

target/i386: Use correct type for get_float_exception_flags() values

The softfloat get_float_exception_flags() function returns 'int', but
in various places in target/i386 we incorrectly store the returned
value into a uint8_t.  This currently has no ill effects because i386
doesn't care about any of the float_flag enum values above 0x40.
However, we want to start using float_flag_input_denormal_used, which
is 0x4000.

Switch to using 'int' so that we can handle all the possible valid
float_flag_* values. This includes changing the return type of
save_exception_flags() and the argument to merge_exception_flags().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250519145114.2786534-3-peter.maydell@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>